Evaluation of the hydrating benefits of a cationic hyaluronic acid: From biological evaluation to consumer home use trial

Active ingredients are often assessed based on physiological measurements, but innovative technologies to measure skin sensations can provide a holistic volunteer assessment of the use of an ingredient. In this paper, the hydrating benefits of a cationic hyaluronic acid (HA) were evaluated alongside clinical biometrics and innovative cognitive measurements to determine how biological benefits correlated with volunteers' feelings and perceptions of hydration. The results demonstrated that cationic HA provides hydrating benefits at the clinical level due to its film-forming properties. Through the use of innovative behavioural measurement tools, we were able to show that these outcomes are perceived by naïve consumers in real-life conditions. In addition, the benefits of cationic HA reported by users were in accordance with the mental representation they had related to the use of HA, thus the product achieved complete sensorial embodiment. We can conclude that the combination of clinical evaluations and home use trials consolidates product assessment when seeking to measure consumer satisfaction with proven biological benefits.

N-acetyl-L-hydroxyproline - A potent skin anti-ageing active preventing advanced glycation end-product formation in vitro and ex vivo

OBJECTIVE

Advanced glycation end-products (AGEs) represent a large group of compounds generated by a non-enzymatic reaction between reducing sugars and amino groups. The formation and accumulation of AGEs in the skin lead to protein crosslinking, dermal stiffening and yellowing, which ultimately contribute to cutaneous ageing. Amino acids have been described to exhibit anti-glycation effects. The objective of this study was to understand the inhibitory role of the amino acid derivative N-acetyl-L-hydroxyproline (NAHP) as an anti-glycation active for human skin.

METHODS

A cell-free assay investigating the inhibition of glycation of serum albumin by NAHP was used to determine the capability of NAHP to decrease AGE formation. Also, by assessing the amount of the AGE N-(carboxymethyl)lysine (CML) the anti-glycation abilities of NAHP were investigated utilizing dot blot analysis. The improvement of cell-matrix interaction by NAHP was determined in vitro using a glycated fibroblast-populated collagen lattice (FPCL) dermis model. In skin biopsies, AGE autofluorescence was determined after treatment with NAHP and/or glucose ex vivo.

RESULTS

NAHP significantly and dose-dependently inhibited levels of AGEs, which were induced by the glycation of a protein solution. This decrease could be visualized by showing that the brownish appearance as well as the AGE-specific fluorescence of glucose-treated samples were reduced after the application of increasing amounts of NAHP. Also, CML formation was dose-dependently inhibited by NAHP. In FPCLs, the contractile capacity of fibroblasts was significantly disturbed after glycation. This could be prevented by the addition of NAHP. Compared to glyoxal-treated samples, the co-application of NAHP significantly decreased the diameter as well as the weight of glycated FPCLs. Ex vivo application of glucose to skin explants showed a higher AGE fluorescence signal compared to control explants. Co-treatment with NAHP and glucose decreased the level of AGE fluorescence in comparison to glucose-treated explants.

CONCLUSION

These data provide clear evidence that under glycation stress conditions treatment with NAHP inhibited AGE formation in vitro and ex vivo and prevented the loss of cellular contractile forces in a glycated dermis model. Thus, NAHP obviously provides a beneficial treatment option to counteract AGE-related changes in human skin such as dermal stiffening and yellowish skin appearance.

A novel Ca2+ double cone vector system to treat compromised skin

BACKGROUND

Stressed, damaged or very aged skin is predominantly characterized by a malfunctioning skin barrier. Underlying skin barrier malfunction is a reduced or defective calcium gradient in the epidermis. Consequently, replenishing the compromised skin's calcium stores with topical calcium could be a potential therapeutic approach.

METHODS

We investigated the effect of our novel Ca2+ double cone vector system on improving the differentiation and barrier function of reconstructed human epidermis (RHE), cultured at low basal calcium (0.3 mM) to represent very aged skin. Furthermore, in a randomized placebo-controlled clinical study the skin barrier of 20 healthy volunteers was challenged with 2% sodium lauryl sulphate (SLS) for 24 h under occlusion, following and/or prior to treatment with a gel containing 2% of our calcium vector system.

RESULTS

Culture in reduced basal calcium conditions (0.3 mM) strongly impeded the formation of a dense stratified epidermis. The apical treatment with 1.1 mM CaCl2 was not able to restore a functional differentiation. Treatment with 0.1% of the Ca2+ delivery system rescued the differentiation process and resulted in a normal stratified epidermis. Clinically, application of the Ca2+ vector system prior to and following SLS stress prevented increases in skin irritation and transepidermal water loss (TEWL) compared to placebo controls. Importantly, the treatment also significantly accelerated the recovery time following SLS stress.

CONCLUSION

With our novel Ca2+ vector system, we highlight the delivery of bioavailable Ca2+ ions into the skin as a new and successful approach to treat a damaged barrier present in stressed, aged or atopic skin.

Efficacy of a wheat polar lipid complex in reducing hair loss and improving hair growth in healthy women: A randomized, double-blind, placebo-controlled clinical study

OBJECTIVE

Hair loss is a major source of psychological distress for affected people. Safe and natural ingredients are therefore needed to help reduce hair loss and stimulate hair growth. This pilot clinical study aimed at exploring the efficacy of a wheat polar lipid complex (WPLC, Ceramosides™), containing sphingolipids and digalactosyl diglycerides, on hair characteristics improvement in women showing acute hair shedding.

METHODS

Sixty-six women presenting a proportion of hair in the telogen phase greater than 15% were recruited and allocated to two groups, each including at least 10 postmenopausal women. For 84 days, participants consumed 30 mg/day of the WPLC supplement, or the placebo. Their hair characteristics were assessed after 56 and 84 days using phototrichogram evaluations of hairs in anagen/telogen phases, measuring hair shedding by a pull test, hair diameter and elongation at break point, hair growth and scalp sebum content. Hair density and volume were also clinically evaluated. All these parameters were also investigated in the subgroup of postmenopausal women.

RESULTS

WPLC supplementation decreased telogen hair density/proportion while increasing the anagen hair density/proportion. These effects were significant compared with the placebo as early as within 56 days. It also led to reduced hair shedding upon pull test analyses. If no changes were evidenced in hair diameter, WPLC improved hair growth and resistance to breakage after 84 days. Clinical evaluations also showed hair density and volume improvement. Furthermore, supplementation decreased scalp sebum content in women with oily hair. The beneficial effects were also observed in the subgroup of postmenopausal women. Finally, WPLC supplementation improved participants' perception of their hair conditions.

CONCLUSION

Through a reducing effect on hair shedding and a stimulating effect on hair reappearance and growth, WPLC dietary supplementation was shown to significantly reduce hair loss in women.

A consumer cross-over trial suggests that there are significant seasonal changes of the tensile properties (wet) of human hair

OBJECTIVES

Through the cooperation with an industrial partner, we gained a set of data for the tensile properties (wet) of human hair. The hair samples originated from a cross-over study with two groups of individuals, using for a topical application sequentially two products (A and B). Each phase of the study lasted 6 months. The phases of the study by chance covered first largely the winter and then the summer period. Initially, tensile variables were chosen, which not only reflect the mechanical properties of hair (modulus, break strain, and break stress) but which are also considered to have a good connection to practice-relevant hair properties. The initial analysis of the data showed that changes were observed for the variables due to the treatment phases. However, these were either small or difficult to interpret.

METHODS

Against this background and using two-factor analysis of variance, we investigated the hypothesis that the tensile properties of hair (wet) may show significant seasonal changes. For this, we chose those two independent variables, which reflect the properties of the intermediate filaments (modulus) and the matrix (break strain) in the composite structure of the hair cortex.

RESULTS

The results support the 'seasonal' hypothesis and clearly show that the variables show significant changes from Winter to Summer (modulus: 10% increase; break strain: 3% decrease). The seasonal effect was thus a major reason, why the first stage of the analysis of the data was inconclusive.

CONCLUSIONS

The tensile properties of the main morphological components of the cortex show distinct seasonal changes. Towards the summer, the hair becomes stiffer and more brittle. Furthermore, the results suggest that seasonal effects may need to be taken into account when conducting studies on lengths of hair grown during different seasons.

Randomized double-blind placebo-controlled cosmetic trial of a topical first-in-class Neutraligand targeting the chemokine TARC/CCL17 in mild-to-moderate atopic dermatitis

BACKGROUND

Atopic dermatitis has a marked economic impact and affects the quality of life. A cosmetic compound with an innovative strategy is proposed here as a small chemical neutraligand, GPN279 (previously identified as a theophylline derivative), that binds and potently neutralizes the TARC/CCL17 chemokine, activating the Th2 cell-expressed CCR4 receptor.

OBJECTIVE

Our objective was to evaluate the safety and activity of topically applied GPN279 in mild-to-moderate atopic dermatitis patients in a randomized, double-blind, placebo-controlled, parallel group trial. Such cosmetic active ingredient targeting dry skin with an atopic tendency would open a parallel strategy to the pharmaceutical approach, in particular for mild to moderate subjects, as an alternative to reduce the evolution towards severe forms of atopy.

METHODS

This 4-week trial included adults with mild-to-moderate atopic dermatitis, according to the SCORAD index. Patients were randomized into two groups treated by topical applications of either an emulsion containing 0.44% GPN279 in placebo on skin lesions or the placebo (4.56% glycerin). Clinical activity was evaluated with the SCORAD as the primary objective. As secondary objectives, POEM, erythema, skin moisturization, its barrier function (TEWL) and safety were evaluated.

RESULTS

Twenty-one patients in each group completed the study. SCORAD was significantly improved in the GPN279 group vs. placebo. GPN279 also significantly improved POEM, induced a rapid and significant decrease of erythema, and improved skin moisture. GPN279 and placebo were well tolerated throughout the study.

CONCLUSION

A cosmetic cream comprising the CCL17 neutraligand GPN279 improved the skin barrier and physiology criteria in patients with mild-to-moderate atopic dermatitis.

Water in cosmetics and Caenorhabditis elegans as an alternative model for lifespan assessment

OBJECTIVE

Water, often considered a fundamental component of life, is the most commonly used ingredient in the formulation of dermocosmetic products, with waterless products being the exception. Dermocosmetic products can contain anywhere from 50% to 85% water, which contributes to their texture and specific characteristics. The chemical composition of water varies depending on its origin and can be categorized as highly mineralized or low mineralized. These compositions could impact the water's efficacy in anti-aging applications. In this study, the objective is evaluating the anti-aging properties of highly and low mineralized water with the model organism Caenorhabditis elegans.

METHODS

In this article, we employed the alternative model organism C. elegans to assess the impact of 5 branded waters, one physiological water and one ultra-pure water on the model's lifespan, using the survival medium conventionally used for C. elegans as a comparison.

RESULTS

Waters may have either a positive or a negative impact on the C. elegans lifespan expectancy. Our results indicate that only one of the water brands we assessed (Volvic®) had a significantly positive effect on worm longevity. In contrast, we found that two other brands (Hepar® and Contrex®) had a negative impact on the later stages of the worm's adulthood. Furthermore, we demonstrated that the impact of the brand water samples on lifespan expectancy varied depending on their physicochemical composition, in particular when ion concentrations were most extreme.

CONCLUSION

This study shows that the highly mineralized waters studied have a detrimental effect on the survival of C. elegans, and a preliminary test with ultra-pure water could not be completed due to its deleterious effect on the worms. This suggests the hypothesis that both highly mineralized and completely demineralized waters may not be the most suitable for skin formulations.

Sunscreens can preserve human skin microbiome upon erythemal UV exposure

OBJECTIVE

Ultraviolet radiation (UVR) is a known environmental key factor for premature skin ageing. Only few scientific evidence is available to support the effects of UVR on the skin microbiome. This in vivo pilot study aimed to evaluate the impact on the skin microbiome upon erythemal UV exposure and the protection of UV-exposed skin microbiome by UV filters.

METHODS

Ten female volunteers were treated with an sun protection factor (SPF) 20 sunscreen and placebo formulation (without UV filters) on their upper middle backs and irradiated with an erythemal dose (2 MED) by a solar simulator. Skin swabbing samples from four zones (i.e., unexposed, exposed, sunscreen- and placebo-treated on exposed skin) were collected for the microbiome analysis before and 2 h after UV exposure, respectively, and processed via shallow 16S rRNA Amplicon and Shotgun metagenomic sequencing. An in vitro UV method was developed to confirm the protection of isolated bacterial strains by single UV filters and combinations.

RESULTS

Alpha diversity was impacted by significant inter-individual differences and by treatment rather than by irradiation. Cutibacterium acnes was found to be the most abundant and a confounding factor for diversity. On a species level, Lactobacillus crispatus was negatively associated with UVR and placebo treatment, whereas there was a positive association with sunscreen treatment. The sunscreen treatment also favoured an interaction network with central Micrococcus genus. The in vitro results showed that both single UV filters and combinations had specific effects on the survival rates of L. crispatus, C. acnes, and Staphylococcus epidermidis.

CONCLUSION

We identified potential microorganisms and bacterial interactions that were associated with an SPF 20 sunscreen treatment. The specific protection of L. crispatus as a key player in the UV-exposed skin microbiome and reduction of C. acnes population by UV filters might lead to new cosmetic concepts for photoprotection.

Deep skin homogeneity and light diffusion: An accelerated Monte Carlo model for in vivo skin characterization and consumer perception

The appearance of healthy and youthful skin is related to many factors of the skin optical properties as perceived by our visual sense. The optics of light travelling through human tissues has been extensively investigated in the field of biomedical applications, including the experimental characterization and modelling of skin optics and the propagation of light such as lasers through the layers. This work presents an innovative approach to probe deep skin by means of spectrally and spatially resolved light diffusion in the different layers of skin. Dual hyperspectral measurements of the panellist's skin are performed in vivo on subjects to obtain reflectance and light diffusion spectra. Both are simultaneously fitted by a GPU-accelerated Monte Carlo model to obtain skin optical parameters as a function of depth. The results show a clear correlation between deep skin light diffusion at wavelengths above 590 nm and the subject age, which indicates a progressive degradation of skin homogeneity with age. The effect of this orange-red light diffusion background is to alter the colour tone of the skin. A skincare product is used to show that the warmer skin colour tone is clearly perceivable to consumers when evaluating facial images with and without the product. The product effect also correlates well with hyperspectral measurements. Lastly, this innovative approach demonstrates a first step in real-time skin characterization for consumers and opens the door to customized cosmetic solutions for individual needs.

Nonclinical evaluation of a Vitis vinifera extract towards a novel antiaging cosmetic ingredient

BACKGROUND

Skin aging is regulated by multiple physiological processes, such as oxidative stress. Natural products have been considered as a promising source of antioxidant compounds. As a result, few innovative products on the market based on natural products tackle additional underlying mechanisms of skin aging.

AIMS

The present work reports the nonclinical evaluation of a novel extract from the skin of V. vinifera fruits (codified as ACH37 extract), with the aim of supporting its use as an antiaging cosmetic ingredient candidate in clinical trials.

METHODS

We employed enzymatic, phenotypic, and gene expression assays, both in vitro and ex vivo, to investigate the action of the ACH37 extract in different biological processes that could be related to skin aging mechanisms.

RESULTS

The ACH37 extract was able to scavenge reactive oxygen species (DPPH, O2 - ), prevent inflammation (LPS- and UV-induced COX-2, IL-1β, and IL-8 expression), modulate extracellular matrix remodeling (inhibiting elastase, MMP-1, MMP-3, and MMP-12, as well as associated expression), increase telomere length, telomerase activity, and reverse the UV-induced suppression of genes involved in skin protection. In addition, the ACH37 extract permeated human skin explants and presented antioxidant efficacy ex vivo.

CONCLUSION

The results indicated that the ACH37 extract acts on multiple targets commonly related to skin aging, being a promising antiaging active ingredient candidate to be further investigated in clinical trials.

Video-based paired comparison to evaluate some cosmetic products under camera movement for dynamic performance

OBJECTIVE

Until now, standardized evaluation of cosmetic effects was conducted mainly in still conditions such as pictures. In real life, the consumers' experience of their cosmetics' effects is dynamic and some of the benefits can be better observed under movement. In order to capture motion-related performance of cosmetics, we developed a video-based paired comparison on an online platform.

METHODS

We validated this new tool through the evaluation of eyeshadow with high light reflection and colour gradation, especially visible under motion according to the observer point of view. This formula was compared with two marketed benchmarks. The three products were applied sequentially on the eyelid of eight Japanese women. Videos were taken in standardized light, speed and face position with a rotating camera around the face. The videos were uploaded on an online secured platform and eyelid 3D effect, highlight and colour gradation were evaluated through paired comparison test by 60 Japanese women from home on their PC or tablets. Those results were compared with picture-based paired comparison by the same observers.

RESULTS

Video-based paired comparison provided higher discrimination of products compared to picture-based comparison.

CONCLUSION

As compared to still camera acquisition, the evaluation of cosmetics based on videos is closer to real-life experience and can bring higher discrimination, especially for motion-related attributes.

A simple and reliable isocratic high performance chromatographic assay for the simultaneous determination of hydrophilic benzophenone-4 and lipophilic octocrylene in sunscreens

OBJECTIVE

This work aimed to develop a simple HPLC method for the simultaneous quantitative determination of the ultraviolet (UV) filters, hydrophilic benzophenone-4 and lipophilic octocrylene, in the presence of three other commonly used UV filters, avobenzone, octisalate, and homosalate.

METHODS

Reverse-phased HPLC was performed on a C18 column. A scouting gradient was initially used to determine the approximate mobile phase composition required for efficient analyte elution and separation before further optimization. The assay was validated with regards to specificity, linearity, intra- and inter-day accuracy and precision, limits of detection and limits of quantification. An ultrasound dispersion extraction method for the UV filters from a commercial sunscreen, was developed and the extraction efficiencies from spiked samples were calculated.

RESULTS

An acetonitrile-methanol-water mixture (20:67:13, v/v/v), where the water component contained 0.2% trifluoroacetic acid (v/v) was found to be the optimal mobile phase at a flow rate of 1.0 mL/min. The assay was linear between 1.0 - 100 μg/mL for both benzophenone-4 and octocrylene (both correlation coefficients were above 0.999). There was no interference from the excipients of the sunscreen nor from the three other UV filters. The intra- and inter-day accuracy was between 90.0 - 104.6% for both analytes. Extraction recoveries from a spiked commercial sunscreen was between 95.4 ± 2.1% to 98.5 ± 2.1% for benzophenone-4, and between 87.3 ± 2.3% and 98.9 ± 3.1% for octocrylene. All validation parameters were within the acceptance criteria set out in the International Council for Harmonization (ICH) guidelines. The HPLC assay showed the extracted quantities of benzophenone-4 and octocrylene from the commercial sunscreen closely matched claimed quantities.

CONCLUSION

The developed isocratic HPLC method was suitable for simultaneously determining the hydrophilic benzophenone-4 and lipophilic octocrylene in the presence of other commonly used UV filters. Additionally, the extraction method was simple and effective for accurately quantifying the UV filters in a commercial sunscreen.

Comparative analysis of original face and skin-warped average face images for the scoring of skin attributes

OBJECTIVES

Representative of a panel, an average face image could be used to analyse/display skin changes while alleviating image rights constraints. Therefore, we used landmark-based deformation (warping) of individual skin images onto their panel's average face, evaluating this approach's relevance and possible limits.

METHODS

An average front face image was constructed from images of 71 Japanese women (50-60 years old). After warping individual skin images onto this average face, the resulting skin-warped average faces were presented to three experts who graded: forehead wrinkles, nasolabial fold, wrinkle of the corner of the lips, pore visibility and skin pigmentation homogeneity. Two experts estimated subjects' age. Results were compared to gradings performed on original images.

RESULTS

Inter-expert grading shows excellent to good correlation whatever image type: from 0.918 (forehead wrinkles) to 0.693 (visibility of pores). Correlations between scoring of both image types are almost always higher than inter-expert correlations (maximum: 0.939 for forehead wrinkles-minimum: 0.677 for pore visibility). Frequencies of grades/ages are similar when scoring original and skin-warped average face images. Experts scores are similar in 90.6%-99.3% of the cases. Average deviations upon scoring both image types are smaller than average inter-expert deviations on original images.

CONCLUSIONS

Scoring facial characteristics in original images and skin-warped average face images show an excellent agreement, even for perceived age, a complex feature. This opens the possibility of using this approach to grade facial skin features, monitor changes over time, and to valorise results on a face deprived of image rights.

Applying sunscreen SPF 50 with high antioxidant capacity during fifteen days improves the dermis echogenicity and reduces the reddish skin undertone

BACKGROUND

Of the many effects induced by UV radiation on the skin, erythema is one of the most well-known features, which is a cutaneous inflammatory reaction correlated with acute photodamage. The utilization of sunscreen may reduce this process.

AIMS

To evaluate the utilization of a sunscreen SPF50 with high antioxidant capacity during 15 days by young men without photoprotection habits.

METHODS

For this, we evaluated erythema, skin hydration properties, and dermis echogenicity using skin imaging techniques. Forty male participants (aged between 18 and 28 years old), 36 without previous photoprotection habits, were recruited, and the erythema was evaluated using a visual score and skin colorimeter. Macroscopic images (VivaCam®) were also obtained. Dermis echogenicity was evaluated using high-frequency ultrasonography. All the participants received a sunscreen SPF 50 to use for 15 days.

RESULTS

The visual score presented a strong correlation (r = 0.8657) with the colorimeter results. Visually and using the biophysical methodologies was possible to observe the reduction of the visual erythema. The dermis echogenicity also improved, probably correlated with the acute inflammation reduction. No alterations were observed in the skin hydration and skin barrier parameters.

CONCLUSIONS

The utilization of complementary and correlated different skin biophysical and imaging techniques in this study allows a better comprehension regarding the skin early photoaging process due the direct sun exposure. The utilization with a SPF 50 sunscreen with high antioxidant potential allows for a reduction in the erythema after 15 days of usage, a quick result, however, did not improved the skin barrier or SC hydration.

A Subjective and Objective Assessment of Combined Methods of Applying Chemical Peels and Microneedling in Antiaging Treatments

Combined methods of applying chemical peels and antioxidants could be an option for skin rejuvenation with no down-time. The penetration of active substances can be enhanced by microneedle mesotherapy. The study was conducted on a group of 20 female volunteers, aged 40-65 years. All volunteers received a series of eight treatments performed every seven days. The whole face was first treated with azelaic acid; following this, the right side received a 40% solution of vitamin C and the left side 10% vitamin C with microneedling. Hydration and skin elasticity were markedly improved, with better results observed on the microneedling side. Melanin and erythema index decreased. No significant side effects were seen. The combination of active ingredients and delivery techniques have great potential to enhance the effectiveness of cosmetic preparations, probably by multidirectional ways of action. In our study, we demonstrated that both 20% azelaic acid + 40% vitamin C treatment and 20% azelaic acid + 10% vitamin C + microneedle mesotherapy efficiently improved the assessed parameters of aging skin. However, the use of microneedling mesotherapy as a means of direct delivery of active compound to the dermis enhanced the effectiveness of the studied preparation.

Functional validation of co-culture model of human keratinocytes and neuronal cell line for sensitive skin by using transient receptor potential channel vanilloid subfamily member 1 antagonist

BACKGROUND

Sensitive skin is a subjective cutaneous hyper-reactivity that occurs in response to various innocuous stimuli. Keratinocytes have recently been shown to participate in sensory transduction by releasing many neuroactive molecules that bind to intra-epidermal free nerve endings and modulate nociception. In the literature, the characterization of these interactions has been based on the co-culture of keratinocyte and mammalian-origin neuronal cell lines. In this study, we established an in vitro model based on a co-culture of primary human keratinocytes and differentiated SH-SY5Y cells, a human neuronal cell line.

METHODS

Human epidermal keratinocytes and SH-SY5Y cells were monocultured and co-cultured. Changes in calcium influx, substance P, inflammatory cytokines, and neuropeptides between the monoculture and co-culture groups treated with capsaicin only and capsaicin with transient receptor potential channel vanilloid subfamily member 1 (TRPV1) antagonist, trans-4-tert-butylcyclohexanol (TTBC), together. In addition, the difference in stinging sensation was evaluated by applying it to the volunteers.

RESULTS

When SH-SY5Y cells were co-cultured with keratinocytes, they had no significant effect on axonal development. Substance P was also released after capsaicin treatment and reduced by TTBC under co-culture conditions. Moreover, the expression of inflammatory cytokines and neuropeptides was significantly increased in co-cultured keratinocytes compared to that under monoculture conditions. In addition, the stinging sensation was significantly induced after the application of capsaicin in vivo and was relieved after the application of the TRPV1 antagonist.

CONCLUSION

We demonstrated that the novel co-culture model is functionally valid through capsaicin and TRPV1 antagonist. We also confirmed that TTBC could be used for the treatment of sensitive skin through a co-culture model and in vivo tests. This co-culture model of keratinocytes and SH-SY5Y cells may be useful in vitro alternatives for studying the close communication between keratinocytes and neuronal cells and for screening therapeutic drugs for sensitive skin.

Learning from hair moisture sorption and hysteresis

OBJECTIVE

The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure.

METHODS

The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered.

RESULTS

By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of "breaking symmetry", derived from moisture sorption-desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulfide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100 %. The analysis suggested that, aside from the glass transition event occurring at around 60-70 % relative humidity, there is another, less examined, transition occurring at around 30 % relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour.

CONCLUSION

The moisture sorption-desorption by hair was shown not only to allow a quantitative differentiation among various cosmetic treatments of the hair, but also to provide valuable information on the structure of the fibre.

Quantification of perception towards facial skin ideal complexion in multiple ethnic populations from clinical imaging cues

OBJECTIVE

Ideal complexion is a perceptual skin quality that is strongly influenced by cultural and ethnic background. The objectives of this study are to quantitatively characterize skin ideal complexion based on clinical image cues and to compare the perceptions of ideal complexion among multiple ethnicities.

METHODS

Facial images of Indian, Chinese, Caucasian and Latino females collected using VISIA®-CR were presented to naïve panels of the same ethnicity following a two-alternative forced choice design and responses on skin "ideal complexion" were obtained from 336 panelists. Panel perception was transformed logistically (d') and projected onto a continuum (ω) following Bradley-Terry model. Image cues including skin color and unevenness, skin shine and surface smoothness, and pigmentary blotches and spots were computed using image analysis and their relationship with ω were evaluated through multiple regression analysis. A novel skin index namely ideal complexion score (ICS) was developed and correlated against age using linear regression. Finally, ICS was applied to evaluate treatment efficacy of a skin brightening kit on 35 female Caucasian subjects.

RESULTS

Panel perception d' showed statistically significant (p < 0.05) correlation with the contrast of image cues for all ethnic panels (R² = 0.74, 0.76, 0.62 and 0.46 for Indian, Chinese, Caucasian and Latino respectively) and strong correlations between perception ω and linear combinations of image cues were observed (R² > 0.88 for all). Main effects of facial image visual cues on ideal complexion were compared: contrast of skin redness and pigmented spots and visual smoothness were important in determining ICS for all ethnicities; skin color unevenness was more pronounced for Indian and Caucasian; skin lightness was important for Indian and Chinese; skin shine was critical for Chinese and Latino; and skin hue angle ranked higher for Caucasian. Correlations between ICS and age were observed for Indian and Caucasian (R² = 0.55) in which ICS decreased as age increased. Twenty-nine percent improvement on ICS was observed after 12 weeks' treatment using the brightening kit compared to the baseline.

CONCLUSION

Mathematical models were successfully established to describe subjective perception towards skin ideal complexion based on objectively measured image cues for multiple ethnicities.

Comparing Hair Tensile Testing in the Wet and the Dry State: Possibilities and Limitations for Detecting Changes of Hair Properties due to Chemical and Physical Treatments

OBJECTIVES

This investigation focusses, first, on the question to which extent wet and dry tensile tests on human hair may be considered as leading to independent results. Second, we try to assess the sensitivities of wet and dry testing to detect changes of mechanical properties. Specifically we were interested in separating changes, which were induced by a combination of a chemical (oxidation/bleach) and a physical treatment (heat).

METHODS

The basis for our study are data for the tensile properties (wet and dry) of a set of untreated and bleached hair tresses, which were submitted to the same schedule of thermal treatments. As characteristic tensile parameters, we chose modulus (E), break extension (BE) and break stress (BS). First, parameters were analysed across treatments for the correlations between wet and dry data. Second, we applied two-factor Analysis of Variance to assess the effects of the factors and their potential interaction.

RESULTS

Correlations for the dry vs wet data show only a weak relationship for E, while coefficients of determination (R² ) are quite high for BE and BS. Two-factor ANOVA enables to quantify the various contributions to the Total Sum-of-Squares for all three parameters. We show that, the parameters respond quite differently to the chemical and the thermal treatments as well as to testing conditions (wet or dry). It is of interest to note that, the interaction between the chemical and the physical treatment is generally quite weak. For the interpretation of the results, we use the concept of the humidity-dependent as well as strain-induced glass transition of the amorphous matrix.

CONCLUSIONS

The independence hypothesis for dry and wet tensile measurements only applies for modulus. Overall, we consider modulus (wet) as the best tensile measure of fibre damage when assessing chemical and/or physical treatments. Under ambient conditions (dry), break stress is shown to be a feasible alternative measure.

5-α reductase inhibition by Epilobioum fleischeri extract modulates facial microbiota structure

Background

Facial skin is a particularly complex environment made of different skin types such as sebaceous (forehead) and dry (cheeks). The skin microbiota composition on different facial sites has not yet been addressed.

Methods

We conducted a 4‐week‐long, single‐centre, randomized and placebo‐controlled clinical study involving 23 Caucasian females. We assessed both bacterial composition on five different facial areas and the microbiome modulatory effects resulting from the topical application of a plant extract (Epilobium fleischeri). Skin microbiome samples were collected before and after 4 weeks of product application. Microbiota profiling was performed via 16S rRNA gene sequencing, and relative abundance data were used to calculate differentials via a multinomial regression model.

Results

Via ‘reference frames’, we observed shifts in microbial composition after 4 weeks of twice‐daily product application and identify certain microbiota species, which were positively associated with the application of the product containing the Epilobium fleischeri extract. Staphylococcus hominis, Staphylococcus epidermidis, and Micrococcus yunnanensis appeared to be significantly enriched in the final microbiota composition of the active treatment group.

Conclusion

Facial skin was found to be colonized by an heterogenous microbiota, and the Epilobium fleischeri extract had a modulatory effect on commensal bacteria on the different facial sites.

Evaluation of aloins, pH and moisture in aloe leaf gel-based personal care products

OBJECTIVE

Some easily applicable analytical methods were explored to evaluate the quality of personal care products containing aloe leaf gel. Aloins should be absent in these products in view of their side effects. To check this, liquid chromatography (LC) was applied.

METHODS

The LC method used a C18 monolithic column combined with gradient elution and ultraviolet (UV) detection. The mobile phase consisted of a mixture of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). The method was validated with respect to specificity, linearity, precision and accuracy. Next, it was practically applied for the analysis of commercial samples. In addition, the pH and moisture content were determined.

RESULTS

The LC results indicated that aloins were detected in 25% of the analysed commercial samples. Further, it turned out that 42% of the test samples were found to be in the basic pH range and 33% of them contained excessive moisture.

CONCLUSION

Proper quality control and adequate labelling of aloe leaf gel-based cosmetics are mandatory to avoid side effects.

Sensitive skin: Active ingredients on the spotlight

OBJECTIVE

Sensitive skin is characterized by self-reported sensory perceptions in response to stimuli that should not provoke unpleasant sensations. Cosmetic products for sensitive skin are designed to minimize these symptoms. This study aimed to unveil the most used active ingredients for sensitive skin in facial care products from the pharmacy and parapharmacy channel.

METHODS

A pool of products from the pharmacy and parapharmacy channel whose label included the expressions 'sensitive skin', 'reactive skin' or 'intolerant skin' were analysed. The active ingredients were identified from product compositions and ranked in descending order of occurrence. The scientific evidence regarding the mechanism of action and efficacy of each ingredient was also compiled.

RESULTS

Eighty-eight products from 19 multinational brands were included. Niacinamide leads the top, followed by Avena sativa, allantoin, glycyrrhetinic acid and derivatives and Laminaria ochroleuca. Ingredients that can reduce skin inflammation and act on the skin barrier were used in more than half of the products analysed. The clinical studies regarding the active ingredients used in these products remain sparse and lack methodological quality. Among the top ingredients, niacinamide, panthenol and acetyl dipeptide-1 cetyl ester were the only ones studied on volunteers having sensitive skin, while acetyl dipeptide-1 cetyl ester and palmitoyl tripeptide-8 were designed to act on the molecular targets involved in this condition.

CONCLUSION

This study reveals the most used active ingredients in cosmetic products for sensitive skin, as well as the scientific evidence supporting their efficacy and the mechanisms of action. This insight is meaningful for dermatologists and other health professionals to provide customized advice based on the symptomatology of individuals with sensitive skin, and for the formulation of cosmetic products and design of new active ingredients.

'All-natural' anti-wrinkle emulsion serum with Acmella oleracea extract: A design of experiments (DoE) formulation approach, rheology and in vivo skin performance/efficacy evaluation

OBJECTIVE

The growing consumers' preferences and concerns regarding healthy ageing, youthful skin appearance, environmental protection and sustainability have triggered an ever-increasing trend towards natural, eco-friendly and ethically sourced anti-ageing products. Accordingly, this paper describes design and evaluation of novel, safe, effective and high-quality emulsion serums, completely based on ingredients of natural origin, intended for improving facial fine lines and wrinkles.

METHODS

Model formulations, stabilized by an innovative glycolipid mixed emulsifier (lauryl glucoside/myristyl glucoside/polyglyceryl-6 laurate) and containing Acmella oleracea extract as a model anti-ageing active, were prepared by cold process and fully assessed regarding their rheological behaviour (continuous rotational and oscillatory tests) and physical stability (dynamic-mechanical thermoanalysis - DMTA test). To study and optimize the simultaneous influence of varied formulation factors (emollients and emulsifier concentrations) on critical rheological attributes of the developed serums, a central composite design within 'design of experiments' approach was employed. The general skin performance - preliminary safety and anti-wrinkle efficacy of selected model serum, was evaluated in human volunteers, by employing several objective, non-invasive bioengineering techniques.

RESULTS

Rheological characterization revealed favourable shear-thinning flow behaviour with yield point, and dominating elastic character (storage modulus G' > loss modulus G") in both amplitude and frequency sweeps, which together with relatively small structural change obtained in DMTA test indicated overall satisfying rheological and stability properties of formulated serums. From the established design space, and taking into account formulation cost and carbon footprint, promising model serum (desired/optimal apparent viscosity, yield point and loss factor, rather small and constant structural change), containing 15% of emollients and 1% of emulsifier, was chosen for in vivo evaluations. Screening of skin irritation effects revealed the absence of potential irritancy of investigated serum, suggesting overall satisfying skin tolerability/preliminary safety. Silicone skin replica image analysis demonstrated noticeable reduction/improvement in all measured skin wrinkle parameters after only 2 weeks of test serum application in periorbital and perioral areas, indicating its rapid and beneficial effects on the facial expression lines and wrinkles.

CONCLUSION

Altogether, the results corroborate the promising potential of the developed Acmella oleracea extract-loaded emulsion serum as safe, effective and non-invasive natural anti-wrinkle product.

Thiamidol containing treatment regimens in facial hyperpigmentation: An international multi-centre approach consisting of a double-blind, controlled, split-face study and of an open-label, real-world study

Objective

Tyrosinase is the rate‐limiting enzyme in melanogenesis. Thiamidol is the most potent inhibitor of human tyrosinase out of 50 000 tested compounds. In clinical studies, it was shown to improve facial hyperpigmentation, post‐inflammatory hyperpigmentation and age spots significantly. To identify the optimal number of daily Thiamidol applications, we conducted a split‐face study comparing the efficacy and tolerability of four‐times with two‐times daily application. Subsequently, we evaluated the efficacy and tolerability of a typical face care regimen containing Thiamidol in a real‐world study.

Methods

The split‐face study was double‐blind, randomized, controlled, including two Thiamidol containing products (serum and day care SPF 30). The serum was applied twice daily on one half of the face and the day care SPF30 twice‐daily on the whole face. The real‐world study was open‐label, observational, including three Thiamidol containing products (day care SPF 30 in the morning, serum and night care in the evening). In both studies, subjects with mild‐to‐moderate facial hyperpigmentation applied the products over 12 weeks. Assessments included clinical and subjective grading of hyperpigmentation, skin condition, hemi‐/modified MASI, chromameter and clinical photography.

Results

In the split‐face study (n = 34), hyperpigmentation, skin roughness and hMASI improved all significantly (P < 0.001) versus baseline, with first visible results after two weeks of twice‐daily application. The four‐times daily application led to significant improvement versus the two‐times daily application. In the real‐world study (n = 83), all evaluated parameters, including skin condition and chromametry (n = 30), improved significantly (P < 0.001) in comparison with baseline and the corresponding preceding visits. The subjects judged the cosmetic properties of the products positively. In both studies, the products were well tolerated.

Conclusion

Four‐times daily Thiamidol improves facial hyperpigmentation significantly more than two‐times daily and is well tolerated by the subjects. The real‐world study with a typical face care regimen containing Thiamidol shows improvement of facial hyperpigmentation and confirms tolerability. Furthermore, the data provide evidence for the suitability of this three‐product Thiamidol regimen for day‐to‐day life.

Understanding humectant behaviour through their water-holding properties

OBJECTIVE

Humectants perform essential roles in the formulation of topical moisturizing products in terms of delivery of active ingredients, consumer experience and biophysical behaviour. How they retain and release water is key to understanding their behaviour.

METHODS

Dynamic vapour sorption (DVS) was used to monitor the dehydration kinetics of three humectants widely used in topical formulations-glycerine, dexpanthenol and urea. Model aqueous solutions with concentrations of 20% w/w were tested and compared against pure deionized water.

RESULTS

The three humectants varied in their ability to retain water during the dehydration process. Dexpanthenol was able to retain water most efficiently during the latter stages of dehydration. Urea demonstrated evidence of crystallization during the final stage of water loss, which was not shown by glycerine or dexpanthenol.

CONCLUSIONS

Humectants perform vital roles in the formulation of consumer acceptable topical products including the delivery of actives to the skin. Their ability to influence water movement in the skin is also essential for the maintenance of stratum corneum flexibility. DVS assessment of aqueous solutions has demonstrated how the behaviour of three commonly used humectants differs. Knowledge of the mechanisms by which these humectants operate enables the formulator to develop topical products optimized for the roles for which they are intended.

Complications of permanent makeup procedures for the eyebrow and eyeline

Japan is one of the few countries that consider the application of permanent makeup a medical procedure, and only doctors and nurses are allowed to perform this procedure. Studies on the safety and esthetic outcomes of permanent makeup procedures are not available, although there are studies that report allergies and other complications associated with permanent makeup. Thus, we aimed to study the complications and esthetic outcomes of permanent makeup.We surveyed clients who underwent permanent eyebrow or eyeline makeup procedures at the Shibuya Mori Clinic between November 2016 and March 2020 using a paper-based questionnaire. The permanent makeup procedures involved inorganic pigments, such as iron oxide and titanium dioxide. The questionnaire consisted of 2 parts: the first part asked whether the clients had experienced persistent redness, itching, swelling, infection, or any other complications (multiple answers possible). The second part used a 5-point Likert scale to rate the clients' satisfaction with the color, shape, and overall appearance of their permanent makeup. We retrospectively studied the clients' responses to survey items.A total of 1352 clients participated in the survey. The median period between the procedure and survey response was 15 days. Overall, complications were reported in 12.1% of cases. The most common complication for each type of procedure was itching for eyebrow procedures (8.2%) and swelling for eyeline procedures (13.2%). Infections were reported in 3 cases (0.2%). None of the post-procedure symptoms persisted until the time of this study. The Likert scale measurements revealed that 89.6% of subjects were satisfied with the aesthetic outcome of their permanent makeup procedure(s).We believe that all symptoms observed in this study were due to needle insertion. No allergies were observed, and the infection rate was quite low (0.2%). Thus, our results suggest that permanent makeup procedures are safe and are associated with high client satisfaction. We must note that the appropriate environment, equipment, and techniques are important prerequisites.

Reduction of telogen rate and increase of hair density in androgenetic alopecia by a cosmetic product: Results of a randomized, prospective, vehicle-controlled double-blind study in men

BACKGROUND

Considerable parts of the global population are affected by androgenetic alopecia (AGA).

AIMS

The efficacy of a foam containing nicotinic acid hexyl ester, polyphenols, zinc, glycine, and caffeine in comparison with a vehicle control foam was assessed in a double-blind vehicle-controlled study in men with AGA over 6 months.

PATIENTS/METHODS

Sixty-two men with AGA were assigned either to the active ingredients (verum) or the vehicle group. They applied the products twice daily on affected scalp areas over 6 months. Automated phototrichograms were obtained at baseline, after 3 and 6 months. In addition, a clinical rating by a dermatologist and by the subjects themselves was documented using standardized questionnaires.

RESULTS

The reduction of the telogen rate from T0 to T6 was significantly stronger in the verum group compared to the vehicle group. The reduction was significant from T0 to T3 and T6 in the verum group, but in the vehicle group only from T0 to T3, not to T6. Significantly increased hair density was noticed in both groups at all time points, but the change from T0 to T6 did not differ significantly between the groups. Cosmetic acceptance of the foam and its application regimen was generally good in both groups. Slight reddening and burning after application of verum in six cases was probably due to the presence of hexyl nicotinate.

CONCLUSION

The study demonstrated a reduction of the telogen rate by a cosmetic foam in men affected by AGA, indicating a benefit for cosmetic intervention against male pattern hair loss.

Comparative sensory and instrumental analyses and principal components of commercial sunscreens

BACKGROUND

The initial contact of consumers when choosing sunscreens is through the trademark, packaging, perfume, and tactile feeling of the product, outlining the popular practice of sensory science.

AIMS

To describe the sensory and physical-mechanical profile of commercial sunscreens through sensory and instrumental analyses related to principal component analysis (PCA).

METHODS

Seven commercial sunscreens available on the Brazilian market and with a solar protection factor (SPF) of 30 were evaluated. Physical-mechanical profiling (rheological and textural analyses) was conducted by a trained panel, followed by sensory profile characterization and descriptive analysis. The results were assessed using the Spearman correlation coefficient and PCA.

RESULTS

The correlation or lack thereof of the instrumental parameters with most of the sensory aspects was demonstrated using the Spearman coefficient. PCA enabled us to identify the nature of the dissimilarities among the samples.

CONCLUSIONS

The obtained results highlight the importance of descriptive sensory analysis in the research and development of sunscreens, evidencing the significance of precisely informing the products' formulation in order to be chosen by the consumer.

Reproducing the scalp microbiota community: co-colonization of a 3D reconstructed human epidermis with C. acnes and M. restricta

OBJECTIVE

A 3D reconstructed human epidermis (RHE) model colonized with specific microbial strains was developed to model the complex interactions between strains of the human scalp hair.

METHODS

Reconstructed human epidermis was colonized with Cutibacterium acnes and Malassezia restricta for 72 h. The epidermal model was characterized in terms of morphology, using immune-labelling targeting biomarkers for barrier structure, proliferation, differentiation and anti-microbial defence. The barrier function was assessed by transepithelial electrical eesistance (TEER) measurements. In order to study the microorganisms on the epidermal model, viable counts and phenotype ultrastructure analysis were performed by scanning electron microscopy (SEM).

RESULTS

The RHE colonized with C. acnes did not lead to severe modifications of the physiological barrier integrity and viability, though it shows aggregates. M. restricta formed large aggregates by a close interaction with the RHE, thus causing both a strong decrease in barrier function and structure degradation and an increased human beta defensin 2 (HBD2) expression. The co-colonized model resulted in barrier depletion, but the overall damage was less severe, respecting the single colonization with M. restricta. The developed 'scalp model' allowed to identify morphological modifications leading to uncontrolled epidermal renewal.

CONCLUSION

This study shows a pre-clinical model that recapitulates the interactions that can occur between site-specific microbial strains and keratinocytes in dandruff condition. The model can be applied to assess ingredients and products' mechanism of action.

A validated photonumeric scale for infraorbital dark circles and its application in evaluating the efficacy of a cosmetic treatment product in a split-face randomized clinical trial

OBJECTIVE

As a result of their complex aetiology and periodicity, dark circles are difficult to characterize and measure, with current assessment techniques relying on specialist equipment, image analysis or proprietary grading scales. There is therefore a need to develop and validate a photonumeric scale for assessing infraorbital dark circles, which can provide an objective and consumer relevant tool for evaluating this condition and the efficacy of treatment products and procedures.

METHODS

A panel of expert clinical evaluators reviewed approximately three thousand facial photographs collected over a 5-year period and selected images representing a dynamic range of dark circles. A 10-point photonumeric scale was created, with corresponding descriptors and images for each grade of the scale. To rigorously validate the scale, linearity, sensitivity and precision were assessed by colorimetry and in-clinic evaluation. Reproducibility was assessed photographically with both experienced and inexperienced clinical evaluators, whereas intragrader repeatability was assessed live in-clinic. The scale was then employed in a split-face randomized clinical trial on 58 subjects to evaluate the efficacy of a cosmetic treatment product over 8 weeks.

RESULTS

Colour analysis of the images showed the scale was linear, with statistically significant correlations observed when colour data (CIElab; Individual Typology Angle) were plotted against the corresponding grades (r > 0.9, P < 0.001). Colour difference (Delta E) was calculated between the infraorbital zone and the surrounding skin, and when data were plotted against the grades, a statistically significant correlation was observed (r = 0.99, P < 0.01). The magnitude of the Delta E suggested that changes in grade are visibly perceptible to the human eye, and therefore, the scale is sensitive and clinically relevant. Intergrader reproducibility showed strong correlation (0.96) and >90% agreement between experienced evaluators, whereas intragrader repeatability assessment showed >90% perfect agreement between grades. Use of this scale in a clinical trial demonstrated the efficacy of a cosmetic product, with a mean statistically significant (P < 0.001) decrease in grade of 0.74 compared to baseline, and 0.59 versus the untreated control, after 8 weeks of treatment.

CONCLUSION

Our photonumeric scale for infraorbital dark circles is sensitive and robust and provides an objective and easy-to-use tool to evaluate dark circles and their treatment.

Targeted dry skin treatment using a multifunctional topical moisturizer

OBJECTIVE

The development of dry skin is a complex process, with a wide variety of factors each playing different roles in its evolution. Given this, it is important when designing a formulation to tackle dry skin that these varied aspects of skin behaviour are addressed. Presented here are the results of a 3-week moisturization study carried out on dry legs. A wide range of traditional and more recently developed biophysical measurement methods have been combined with visual assessment of skin condition to enable multiple aspects of skin function to be determined. The observed changes in the skin are discussed in terms of the ingredients used in the moisturizing formulation.

METHODS

A range of novel and traditional skin assessment methods and techniques were used to assess the effects of an oil in water-based moisturizing product compared to an untreated site during a 3-week in vivo study on dry lower leg skin.

RESULTS

Statistically significant improvements were observed in a range of skin parameters as a result of product usage. Skin hydration assessed using Corneometer®, Epsilon® and visual dry skin grading all increased after 3 weeks of use. Skin barrier function measured using transepidermal water loss also improved. Levels of cholesterol, free fatty acids and Ceramide NH increased, as well as the average length of the stratum corneum (SC) lipid lamella bilayers, and the ratio of lipid to protein increased (measured using Lipbarvis® and in vivo Confocal Raman Spectroscopy). Increases in the levels of Ceramide EOS and NP were also observed, along with an improvement in corneocyte maturity, although these were not statistically significant.

CONCLUSIONS

Using a variety of traditional and novel skin assessment techniques, a wide range of factors associated with the evolution of dry skin have been assessed upon treatment with a new topical moisturizer. Product usage resulted in significant improvements to skin hydration and barrier function, the levels and morphology of SC barrier lipids, and overall epidermal differentiation. As a result there was a significant reduction in the characteristics associated with the development of dry skin after use of the test product.

Quantitative ion determination in eccrine sweat gland cells correlates to sweat reduction of antiperspirant actives

OBJECTIVE

Axillary wetness represents an unwanted effect of the physiologically vital sweating mechanism, especially when it becomes excessive. Cosmetic products reducing sweat secretion rely on aluminium salts as the active ingredient acting by physically blocking the sweat gland. Driven by the interest to better understand the sweat mechanism and to develop alternative technologies against excessive sweating a search for an effective testing approach started as up to now, cost- and time-consuming in vivo studies represent the standard procedure for testing and identifying these alternatives.

MATERIAL AND METHODS

The herein described in vitro test system is based on the measurement of intracellular changes of the ion equilibrium in cultured eccrine sweat gland cells. Subsequently, in vivo studies on the back of volunteers were conducted to verify the sweat-reducing effect of in vitro newly discovered substance.

RESULTS

In this study, we describe an effective cell-based in vitro method as a potent tool for a more targeted screening of alternatives to aluminium salts. Testing the commonly used aluminium chlorohydrate as one example of an aluminium-based active in this screening procedure, we discovered a distinct influence on the ion equilibrium: Intracellular levels of sodium ions were decreased while those of chloride increased. Screening of various substances revealed a polyethyleneimine, adjusted to pH 3.5 with hydrochloric acid, to evoke the same alterations in the ion equilibrium as aluminium chlorohydrate. Subsequent in vivo studies showed its substantial antiperspirant action and confirmed the high efficiency of the polyethyleneimine solution in vivo. Further, specific investigations connecting the chloride content of the tested substances with the resulting sweat reduction pointed towards a substantial impact of the chloride ions on sweating.

CONCLUSION

The newly described in vitro cell-based screening method represents an effective means for identifying new antiperspirant actives and suggests an additional biological mechanism of action of sweat-reducing ingredients which is directed towards unbalancing of the ion equilibrium inside eccrine sweat gland cells.

Facial radiance influences facial attractiveness and affective impressions of faces

Objective

Facial attractiveness has been reported to be influenced by visual features such as facial shape and the colour and texture of the skin. However, no empirical studies have examined the effects of facial skin radiance on facial attractiveness. The present study investigated whether types of skin reflection (i.e. radiant, oily and shiny, and matte) and the position of the reflection on the face influence facial attractiveness and other affective impressions.

Methods

A total of 160 female participants (1) estimated the ages and (2) evaluated attractiveness and other impressions of unfamiliar female faces in a total of seven skin reflection conditions. These conditions incorporated three types of reflection (i.e. radiant, oily and shiny, and matte) and three positions of the reflection on the face (i.e. entire facial skin, only cheeks, and only T‐zone).

Results

The facial images of radiance on entire faces were rated as appearing younger than the facial images of oily shine on entire faces and the matte faces. Attractiveness ratings and other positive impressions increased in the order of the matte (ranked lowest), the oily shine on entire face, and the radiance on entire face (ranked highest) conditions. The reflection position also influenced facial attractiveness: attractiveness ratings and other positive impressions were higher in the radiance on entire face condition than in the radiant cheeks and the radiant T‐zone conditions. Interestingly, the radiant cheek faces were rated more radiant and healthier but less feminine and less bright than the radiant T‐zone faces.

Conclusion

These results suggest that facial radiance enhances facial attractiveness and conveys a wide variety of positive impressions on the observer. The magnitude of the effects of cheek radiance and T‐zone radiance differs across various affective impressions. Nevertheless, the results demonstrate that cheek and the T‐zone radiance both contribute to higher attractiveness and other positive impressions of the radiance on entire faces. We believe that our findings can contribute as a guide to the enhancement of positive facial impressions by means of skin radiance, thereby leading to a better understanding of the value of skincare and base makeup.

Topical odorant application of the specific olfactory receptor OR2AT4 agonist, Sandalore® , improves telogen effluvium-associated parameters

BACKGROUND

Human hair follicles (HFs) express the olfactory receptor (OR)2AT4, which is selectively stimulated by the synthetic sandalwood-like odorant, Sandalore^® . In organ-cultured, human scalp HFs, Sandalore^® prolongs anagen and suppresses apoptosis by up-regulating intrafollicular IGF-1 mediated signaling.

AIMS

The objective of this study is to demonstrate whether effects of Sandalore^® observed ex vivo translate into a clinically relevant effect in patients with telogen effluvium.

PATIENTS/METHODS

In a randomized, double-blinded, placebo-controlled, clinical trial, 60 female volunteers (18-65 years) affected by telogen effluvium received over a period of 24 weeks treatment with either 1% Sandalore^® solution (n = 30) or placebo (identically smelling, but non-OR2AT4 activating sandalwood oil n = 30). The study read-out parameters were the degree of hair shedding, hair volume, terminal/vellus hair ratio, anagen/catagen-telogen ratio, and patient self-assessment.

RESULTS

Sandalore^® 1% ameliorated clinical signs of telogen effluvium, namely it reduced hair shedding, and increased hair volume and the percentage of anagen HFs, the latter two parameters significantly more than placebo when changes were calculated to baseline. Sandalore^® also increased the ratio of terminal/vellus hairs at week 8. Most of the anti-hair shedding effects were seen after 8 weeks and maintained at week 24. Patient questionnaire showed that verum group patients were more satisfied than the placebo group in regard to the overall results.

CONCLUSION

This clinical trial supports previous findings of anagen-prolonging effects of Sandalore^® ex vivo with similar results now reproduced in clinical practice. It also provides proof-of-principle that a topically applied cosmetic odorant acting through HF olfactory receptors can be a therapeutic alternative to treat hair loss disorders characterized by excessive hair shedding such as telogen effluvium.

Prediction of treatment effect perception in cosmetics using machine learning

Perception of treatment effect (TE) in cosmetics is multifaceted and influenced by multiple parameters that need to be considered simultaneously when evaluating TE. Here we provide a global approach to predicting TE perception using Random Forest (RF) classifier. Data from three randomized double-blind clinical studies with a total of 50 subjects were used. Different products were applied to each facial cheek of subjects at each visit, and post-application photographs were taken. Nine primary endpoints relating to skin pores were assessed by a specific image analysis algorithm. Twenty judges evaluated the relative pore visibility in all possible pairs of cheek photographs. RF was used to construct a prediction model for TE perception based on the primary endpoints and judge's evaluation. Intra-study product ranking was done using the Bradley-Terry model on mean judges' predicted preference. RF demonstrated overall good accuracy in predicting TE perception. Applying RF technique not only addresses issues of multiplicity, nonlinearity and interactions between multiple criteria but also focuses decision-making on one discrete parameter thereby simplifying interpretability and allowing for more consumer-centered claim substantiation in clinical trials.Abbreviations: RF: Random Forest classifier; FDA: The US Food and Drug Agency; ID: Identifier; MCID: Minimal clinical important difference; Param: Parameter; PGIC: Patients' Global Impression of Change; TE: Treatment effect; TRT: Treatment.

Eriodictyon angustifolium extract, but not Eriodictyon californicum extract, reduces human hair greying

OBJECTIVE

Yerba Santa (Eriodictyon angustifolium and Eriodictyon californicum) has been used for many years in traditional medicine. However, the effect of Yerba Santa on melanogenesis has not yet been investigated. We aimed to assess the biological effects of Yerba Santa on hair pigmentation.

METHODS

Yerba Santa extracts were assessed for their cytological effects following X-ray irradiation treatment and then tested directly for the prevention of human hair greying. Ultra-performance liquid chromatography (UPLC) was utilized to identify the individual extract components.

RESULTS

Eriodictyon angustifolium extract significantly increased melanin synthesis in the melanoma cell line through activation of the WNT/MITF/tyrosinase-signalling pathway. In contrast, E. californicum had no effect on melanin synthesis. E. angustifolium extract also demonstrated a protective effect against the damage induced by X-ray irradiation in human keratinocytes. Application of the extracts to subjects who had grey beards demonstrated a reduced number of grey beard hair per year specifically with the E. angustifolium extract. A significant decrease in grey head hair was also observed after application of E. angustifolium extract. Upregulation of gene expression related to melanin production and WNT signalling was observed after the application of E. angustifolium extract. Sterubin was the most abundant flavonoid detected by UPLC in E. angustifolium extract. In addition, sterubin showed the highest difference in terms of quantity, between E. angustifolium and E. californicum extract.

CONCLUSION

Eriodictyon angustifolium extract, which is abundant in sterubin, may be suitable as a potential cosmetic and medical agent for the prevention and improvement of hair greying.

An image-based mapping of significance and relevance of facial skin colour changes of females living in Thailand

Objective

There are methods to evaluate skin colour on defined areas over the face but no approach automatically and accurately evaluates skin colour variations on large facial areas, comparing subjects, treatments and/or time points. We propose such an image‐based approach to visualize quickly the outcome of clinical studies on colour variations.

Methods

Among 54 Asian women, one group applied a vehicle twice daily, during 28 days, and the other group an anti‐ageing emulsion, taking facial images at baseline and after treatment. Changes in L*a*b* values were studied on four pre‐selected facial regions. We also reconstructed average facial images from which the L*a*b* parameters were extracted for every pixel, computing relevance (ΔE) and significance data. Using colour gradients, we mapped these results onto the average facial images.

Results

After treatment, L*a*b* parameters show no statistically relevant colour changes in the vehicle group. In the ‘active’ group, skin was lighter at the upper cheek and, overall, redness decreased. Relevance and significance maps confirmed no visible colour changes in the vehicle group. In the ‘active’ group, the mapping approach revealed colour changes and their location. Skin became lighter below the eye, cheek and forehead. It was less red below the eyes, on the cheek, jawline and forehead, and generally more yellow.

Conclusion

Our image‐based mapping approach proves to be powerful. It enables us to identify precise facial regions of relevant and statistically significant colour changes after a topical treatment, regions that would have otherwise been undetected.

Facial skin mapping: from single point bio-instrumental evaluation to continuous visualization of skin hydration, barrier function, skin surface pH, and sebum in different ethnic skin types

Dry skin is one of the most important concerns of consumers worldwide. Despite huge efforts over several decades, the personal care industry still does not offer a perfect solution to satisfy the unmet needs of consumers for moisturising treatments in different ethnic groups. The paucity of data for the underlying cellular and biochemical problems in, and the effects of moisturisers on photodamaged facial skin may partly explain this. Mainly, single point measurements are used to understand the effects of products on skin physiology even on surrogate skin sites such as the non‐photodamaged volar forearm. Some groups have developed discontinuous facial maps of skin biophysical properties, however, in 2014 a continuous facial analysis of bio‐instrumental evaluations was developed using a heat map approach. These maps enabled a continuous visualization of features that not only revealed an unexpected complexity of facial skin but also indicated that use of surrogate skin sites for facial skin is inappropriate. We have demonstrated that remarkable gradients of skin hydration, TEWL, skin surface pH and sebum exist within short distances across the face and the gradients are distinctive among different ethnic groups. In addition, these studies have demonstrated that darkly‐pigmented individuals do not necessarily have a better skin barrier function than their less‐pigmented counterparts and that Caucasians have a lower facial skin surface pH compared with more pigmented subjects. Overall, there are no correlations between capacitance, TEWL and skin surface pH including individual topology angle values. Novel 3D camera approaches have also been used to facilitate a more precise assignment of measurement sites and visualisation. The 3D facial colour mappings illustrated precisely the local moisturising effects of a moisturising cream. There were subtle ethnic differences in efficacy that may be related to underlying skin biochemistry and/or ethnic differences in product application. A placebo‐controlled study using conductance measurements in Chinese subjects is also reported. Finally, a new whole face statistical approach has been taken to prove differences in skin parameters but also of moisturiser treatment that adds further to our understanding of the ethnic differences in skin physiology and product application. This paper reviews the background of the development and application of this methodology.

Anti-inflammatory / anti-oxidant activity of ingredients of sunscreen products? Implications for SPF

OBJECTIVE

The Sun Protection Factor (SPF) of sunscreen products is derived from testing in vivo their ability to prevent erythema ("sunburn"). Recently, certain articles have raised concerns that sunscreen products may actively suppress erythema via anti-inflammatory / anti-oxidant (AI/AO) activity. These articles reason that this may result in a higher labelled SPF value than that provided by the efficacy of the UVR filters alone, giving consumers a "false sense of security". On the other hand, since inflammatory processes are known to play a role in the mechanisms of photodamage / skin cancer induction and propagation, AI/AO activity may provide valuable incremental photoprotective benefit (provided that there is no interference with visible erythema). The objective of these studies, therefore, was to investigate the potential of AI/AO ingredients to suppress UVR-induced erythemal response in human skin, in vivo.

METHODS

In vivo studies with SPF30 sunscreen formulations containing a variety of AI/AO ingredients were performed according to the International Standard ISO24444:2010 method. While ISO24444:2010 requires assessment of erythema at 20 ± 4h post-irradiation, an additional assessment at 5 h post-irradiation was also used to determine potential delay in erythema development.

RESULTS

None of the formulations, containing a variety of AI/AO ingredients, influenced SPF determination in comparison to the vehicle formulation.

CONCLUSION

Our in vivo results demonstrate that commonly-used AI/AO ingredients, at concentrations typically used in sunscreen products, neither influence SPF value nor delay erythemal response, i.e., the measured SPF reflects the true photoprotective capacity of the product.

Prediction of skin anti-aging clinical benefits of an association of ingredients from marine and maritime origins: Ex vivo evaluation using a label-free quantitative proteomic and customized data processing approach

BACKGROUND

The application of ingredients from marine and maritime origins is increasingly common in skin care products, driven by consumer expectations for natural ingredients. However, these ingredients are typically studied for a few isolated in vitro activities.

OBJECTIVES

The purpose of this study was to carry out a comprehensive evaluation of the activity on the skin of an association of ingredients from marine and maritime origins using label-free quantitative proteomic analysis, in order to predict the clinical benefits if used in a skin care product.

METHODS

An aqueous gel containing 6.1% of ingredients from marine and maritime origins (amino acid-enriched giant kelp extract, trace element-enriched seawater, dedifferentiated sea fennel cells) was topically applied on human skin explants. The skin explants' proteome was analyzed in a label-free manner by high-performance liquid nano-chromatography coupled with tandem mass spectrometry. A specific data processing pipeline (CORAVALID) providing an objective and comprehensive interpretation of the statistically relevant biological activities processed the results.

RESULTS

Compared to untreated skin explants, 64 proteins were significantly regulated by the gel treatment (q-value ≤ 0.05). Computer data processing revealed an activity of the ingredients on the epidermis and the dermis. These significantly regulated proteins are involved in gene expression, cell survival and metabolism, inflammatory processes, dermal extracellular matrix synthesis, melanogenesis and keratinocyte proliferation, migration, and differentiation.

CONCLUSIONS

These results suggest that the tested ingredients could help to preserve a healthy epidermis and dermis, and possibly to prevent the visible signs of skin aging.

Spectroscopy as a tool to evaluate hair damage and protection

OBJECTIVE

Methods that can be used to analyse hair damage and to support a claim of hair protection are important for the cosmetic industry. There are many approaches available, but they are usually laborious and expensive. The researchers propose a simple fluorescence method that is based upon the emissive properties of damaged hair.

METHODS

Hair fluorescence was observed when using both fluorimetry and microscopic procedures. The method was developed by comparing native hair with hair that was damaged by UVA and visible light.

RESULTS

Spectroscopic properties (absorption and emission) of hair in the visible range are presented. The changes in the emissive properties of hair during irradiation were characterized and they were correlated with photobleaching, which is due to the generation of singlet oxygen. Emissions were also obtained in the hair shafts that had been previously treated with chamomile extract and this treatment was able to avoid hair bleaching.

CONCLUSION

The emissive properties of hair in the visible range can be used as a tool for the evaluation of hair damage and protection. This method can be useful as a tool in order to claim substantiation.

Defining and validating a Body Skin Discomfort Index (BSDI)

OBJECTIVE

To understand the drivers of body skin discomfort and to validate a new index to assess its severity. This index should be sensitive enough to capture changes in response to treatment.

METHODS

Previous consumer studies suggested seven potential main dimensions behind skin discomfort. Four of them refer to self-declarations (stinging, itching, warming and tightening), whereas three can be assessed by a dermatologist (skin dryness, redness and desquamation). Intensity and frequency or extent of these items were measured using 0-9 ordinal scales. To generate the data for validation of a new index based on the 7 items, a group of 49 subjects complaining of skin discomfort was followed up for 5 weeks: 1-week without product application to check reproducibility, followed by 4 weeks of treatment to evaluate sensitivity to change. Items not significantly reported at baseline or with changes because of treatment not sufficiently correlated with the overall change measured by the index were discarded. A control group of 49 subjects presenting no discomfort at all was also included to check the capacity of our index to discriminate both groups. The final index (Body Skin Discomfort Index, BSDI) was normalized to facilitate the clinical interpretation of the results.

RESULTS

After discarding warming and skin redness, the BSDI is finally a five-dimension score calculated as follows: (TI + TF + SI + SF + ItI + ItF + DI + DE + DqI + DqE) 9 9/90 where T, S, It, D and Dq refer to tightness, stinging, itching, dryness, desquamation respectively, and I, F or E refers to intensity, frequency or extent. The final BSDI score displayed a good capacity to discriminate people with skin discomfort from people with 'normal skin', a good reproducibility (intraclass coefficient correlation ICC = 0.85) and a good sensitivity to detect change because of treatment (Difference vs. Baseline of 2.63 on a 0-9 scale).

CONCLUSION

The developed index, BSDI, is a reliable way to address the measurement issue of the multidimensional skin discomfort syndrome. It thus should simplify the evaluation of cosmetic products effect and helps to compare products dedicated to body cleansing.

Predicting lipstick sensory properties with laboratory tests

OBJECTIVE

Sensory perceptions and performance are important to the success of a lipstick formulation, but in vivo evaluation can be expensive and time-consuming. The goal of this work was to develop and use laboratory test methods to predict the sensory and performance properties of lipstick.

METHODS

Twelve model lipstick formulations were prepared, in which only the emollient varied, resulting in a variety of sensory and performance properties. The lipsticks were tested for sensory perceptions of spreadability, stickiness, opacity and gloss with a nine-person panel. The performance properties were evaluated with a friction test using a CETR UMT-2 tribometer, an application test using an analytical balance, a tack test using a Texture Analyser TA.XT-Plus and a colour development/retention test using photography and image analysis. The results of the laboratory tests were compared with the results of the sensory panel using statistical modelling.

RESULTS

The results of the laboratory tests correlated well with the measured sensory properties. The results of the friction test classified the lipsticks into four groups, which were termed oily, creamy, waxy and sticky; these classifications were also evident in the other laboratory test data. Surprisingly, it was found that the friction test could be used alone to predict all the measured sensory properties with statistical models. The correlation between the coefficient of friction and the measured sensory properties is explained by the balance of adhesive and cohesive properties of the lipstick. These properties are influenced by the emollient and affect the application properties and resulting film.

CONCLUSION

The emollient has a significant effect on the sensory and performance properties of a lipstick, which can be predicted with the developed laboratory tests. Furthermore, the friction test can be used to sufficiently predict four important lipstick sensory attributes: spreadability, stickiness, opacity and gloss. Using the methods presented here, lipstick formulations may be more rapidly developed and optimized.

The in vitro antimicrobial evaluation of commercially essential oils and their combinations against acne

OBJECTIVE

The study investigated the efficacy of commercial essential oil combinations against the two pathogens responsible for acne with the aim to identify synergy and favourable oils to possibly use in a blend.

MATERIALS AND METHODS

Antimicrobial activity was assessed using the minimum inhibitory concentration (MIC) assay against Staphylococcus epidermidis (ATCC 2223) and Propionibacterium acnes (ATCC 11827), and the fractional inhibitory concentration index (ΣFIC) was calculated. Combinations displaying synergistic interactions were further investigated at varied ratios and the results plotted on isobolograms.

RESULTS

From the 408 combinations investigated, 167 combinations were identified as displaying noteworthy antimicrobial activity (MIC value ≤1.00 mg mL-1 ). Thirteen synergistic interactions were observed against S. epidermidis, and three synergistic combinations were observed against P. acnes. It was found that not one of the synergistic interactions identified were based on the combinations recommended in the layman's aroma-therapeutic literature. Synergy was evident rather from leads based on antimicrobial activity from previous studies, thus emphasizing the importance of scientific validation. Leptospermum scoparium J.R.Forst. and G.Forst (manuka) was the essential oil mostly involved in synergistic interactions (four) against S. epidermidis. Cananga odorata (Lam.) Hook.f. and Thomson (ylang ylang) essential oil was also frequently involved in synergy where synergistic interactions could be observed against both pathogens. The combination with the lowest MIC value against both acne pathogens was Vetiveria zizanioides Stapf (vetiver) with Cinnamomum verum J.Presl (cinnamon bark) (MIC values 0.19-0.25 mg mL-1 ). Pogostemon patchouli Benth. (patchouli), V. zizanioides, C. verum and Santalum spp. (sandalwood) could be identified as the oils that contributed the most noteworthy antimicrobial activity towards the combinations. The different chemotypes of the essential oils used in the combinations predominantly resulted in similar antimicrobial activity.

CONCLUSIONS

The investigated essential oil combinations resulted in at least 50% of the combinations displaying noteworthy antimicrobial activity. Most of the synergistic interactions do not necessarily correspond to the recommended layman's aroma-therapeutic literature, which highlights a need for scientific validation of essential oil antimicrobial activity. No antagonism was observed.

Understanding the effects of topography on skin moisturization measurement via two-dimensional capacitance imaging

OBJECTIVE

Methods which assess skin moisturization based on changes in its electrical properties are widely used in both cosmetic and medical research industries. However, the devices themselves often give results which are significantly different to each other. Recently two-dimensional imaging moisturization systems have become commercially available, which have the capability to provide a more detailed assessment of what is contributing to measured skin moisturization. Presented here is a new in vitro method for preparing textured model test substrates for use with these devices, and results of their use to provide a clearer insight into the devices operation.

METHODS

A variety of different textured model test substrates were measured using a commercially available skin moisturization measurement device, the Epsilon. The response of the Epsilon was also tested against conventional skin moisturization devices.

RESULTS

Surface morphology of model test substrates was found to have a significant influence on the measurement of its electrical properties with both the conventional and two-dimensional skin moisturization measurement devices. Through modification of the areas of the image being assessed for the two-dimensional moisturization mapping device, the parts of the model test substrate in contact with the device were indentified and analysed separately to areas not in contact with the sensor. This provided a more robust assessment of the electrical properties of substrate itself, rather than being influenced by texture like the conventional skin moisturization measurement devices.

CONCLUSIONS

While the two-dimensional moisturization mapping systems can be used like a conventional electrical skin measurement device giving a simple overall reading of skin moisturization for the test area, their true value over existing electrical measures comes from its ability to isolate the skin itself from areas which are not in contact with the sensor.

Objective measurements of skin surface roughness after microdermabrasion treatment

BACKGROUND

The aim of this article is to present a new methodology for assessment of skin topology using a three-dimensional image (3D).

METHODS

The measurement of the skin surface roughness is based on 3D scanning of silicone replicas by chromatic aberration length technique in a contactless manner, i.e. by a polychromatic light beam. Analysis of the skin surface reprints was performed using Talymap, Gold version. Results were analysed by fractal geometry, which allows to evaluate changes of the skin surface before and after application of cosmetics and instrumental cosmetological techniques. The methodology was applied for objective assessment of the effects of diamond microdermabrasion on the skin surface roughness. Measurements were performed on 23 volunteers in the age group of 31-67 years.

RESULTS

Based on the results of skin surface scanning after the treatment with diamond microdermabrasion it may be concluded that inequalities of the skin surface are reduced immediately after exfoliation. However, this effect mostly diminishes within 14 days after treatment. The entire study ultimately suggests that the instrumental method used only leads to improvement of the skin surface immediately after its application. Thermo vision images of the skin surface temperature were obtained during the application of the abrasive method. The experimental results showed that the skin is rather cooled than heated by the treatment.

CONCLUSION

This study is focused on the development of a methodology for objective measurement of changes in treated skin relief using 3D scanning. The results are evaluated using fractal dimension. The output may also include also an enlarged model of the skin surface made by 3D printer, which can serve for illustrative communication with the client.

Self-preserving personal care products

OBJECTIVE

As questions on the safety of some popular preservatives are on the rise, there is a growing interest in developing 'self-preserving' personal care products. Use of multifunctional ingredients/actives with antimicrobial properties has been explored as replacements for conventional preservatives. This study explores the use of combinations of multifunctional actives (MFA) and other cosmetic ingredients in various personal care formulations, to deliver microbiologically safe self-preserving products. Products studied in this study include face wash, gel-based leave-on skin care product and face mask.

METHODS

Minimum inhibitory concentration (MIC) of several cosmetic ingredients was determined to identify multifunctional actives with antimicrobial activity. Personal care formulations made with multifunctional actives and other cosmetic ingredients were studied for preservative efficacy by challenging the product with six multiple cycles of microbial challenge.

RESULTS

Formulations with combinations of multifunctional actives with antioxidant (AO) and chelators (CHL) were found to work synergistically and were highly efficacious in controlling multiple microbial challenges as observed in the preservative efficacy test (PET) studies. The effective combinations were able to withstand up to six multiple microbial challenges without product degradation. The preservative efficacy profile was similar to control formula containing preservatives.

CONCLUSION

Self-preserving personal care/cosmetic products can be developed which are as efficacious as preserved products by a prudent selection of multifunctional actives, antioxidants and chelators as a part of the formulation.

Electron microscopic investigation and elemental analysis of titanium dioxide in sun lotion

OBJECTIVE

The objective of this research was to determine the size, shape and aggregation of titanium dioxide (TiO₂ ) particles which are used in sun lotion as UV-blocker.

METHODS

Overall, six sunscreens from various suppliers and two reference substances were analysed by electron microscopy (EM) techniques in combination with energy dispersive X-ray spectroscopy (EDS). Because of a high fat content in sun lotion, it was impossible to visualize the TiO₂ particles without previous EM sample preparation. Different defatting methods for TiO₂ from sun screens were tested. A novel sample preparation method was developed which allowed the characterization of TiO₂ particles with the help of EM and EDS.

RESULTS

Aggregates of titanium dioxide with the size of primary particles varying between 15 and 40 nm were observed only in five products. In the sun lotion with the highest SPF, only few small aggregates were found. In the sun screen with the lowest SPF, the largest aggregates of TiO₂ particles were detected with sizes up to 1.6 μm. In one of the sun lotions, neither TiO₂ nor ZnO was found in spite of the labelling. Instead, approx. 500 nm large diamond-shaped particles were observed. These particles are composed of an organic material as only carbon was detected by EDS.

CONCLUSION

A novel defatting method for sample preparation of titanium dioxide nanoparticles used in sun cosmetics was developed. This method was applied to six different sun lotions with SPF between 30 and 50+. TiO₂ particles were found in only five sunscreens. The sizes of the primary particles were below 100 nm and, according to the EU Cosmetic Regulation, have to be listed on the package with the term 'nano'.

Understanding effects of topical ingredients on electrical measurement of skin hydration

OBJECTIVE

Methods that assess skin hydration based on changes in its electrical properties are widely used in both cosmetic and medical research. However, the devices themselves often give results which are significantly different to each other. Although some work has previously been carried out to try and understand what these devices are actually reading, it was based on a technique for measuring the devices' responses to filter discs impregnated with different liquids, which could in itself be influencing the measurements. Presented here is a new method for measuring the devices' direct responses to different materials and solutions which removes any other confounding effects, thereby providing a clearer insight into their operation.

METHODS

The responses of a variety of different liquids and solutions were measured using the Corneometer^® and Skicon^® . A new method is presented, based on the use of a custom-designed PTFE block to hold the liquids, allowing their measurement without using a filter paper. This method was developed and tested against the existing filter paper-based approach.

RESULTS

Differences were observed in results between filter paper- and PTFE block-based approach, indicating that the filter paper itself is capable of influencing the measurements and as such is not to be recommended for assessing how different liquids impact on results from the devices. A positive correlation was observed between Corneometer^® and Skicon^® readings for certain solutions and under certain conditions. A large influence of salt concentration was noted for the Skicon^® device with no or minimal impact from the actual water itself, humectants and emollients. Salts, emollients, water and humectants were observed to have an effect on Corneometer^® readings.

CONCLUSIONS

Both the Corneometer^® and Skicon^® were influenced to different extents by chemicals other than water and therefore cannot be seen purely as measures of skin 'hydration'. Although there is strong evidence that the devices do correlate with expert assessment of skin dryness, the level of water in the skin is only part of the story when it comes to understanding the benefits of topical moisturizing products applied to the skin. An alternative approach would be to consider skin 'moisturization' as a property which is influenced by water, salts and other materials such as humectants and emollients, which is more consistent with how the stratum corneum itself helps to maintain its plasticity and flexibility. In the work presented here, the Corneometer^® was more suited to providing a measurement which reflects the impact of multiple different components.