Itching sensation and neuronal sensitivity of the skin

Extraction, Purification, Structural Characteristics, Biological Activity and Application of Polysaccharides from Portulaca oleracea L. (Purslane): A Review

Portulaca oleracea L. (purslane) is a widely distributed plant with a long history of cultivation and consumption. Notably, polysaccharides obtained from purslane exhibit surprising and satisfactory biological activities, which explain the various benefits of purslane on human health, including anti-inflammatory, antidiabetic, antitumor, antifatigue, antiviral and immunomodulatory effects. This article systematically reviews the extraction and purification methods, chemical structure, chemical modification, biological activity and other aspects of polysaccharides from purslane collected in the Chinese Pharmacopoeia, Flora of China, Web of Science, PubMed, Baidu Scholar, Google Scholar and CNKI databases in the last 14 years, using the keywords "Portulaca oleracea L. polysaccharides" and "purslane polysaccharides". The application of purslane polysaccharides in different fields is also summarized, and its application prospects are also discussed. This paper provides an updated and deeper understanding of purslane polysaccharides, which will provide useful guidance for the further optimization of polysaccharide structures and the development of purslane polysaccharides as a novel functional material, as well as a theoretical basis for its further research and application in human health and manufacturing development.

Cowhage-induced itch scores and the current perception threshold in assessing sensitive skin: An observational laboratory study

BACKGROUND

The diagnosis of sensitive skin remains nonuniform, and the underlying mechanism is unclear. Previous studies were inconsistent in the current perception threshold (CPT) measurement for sensitive skin; thus, the neural sensitivity of sensitive skin needs to be clarified.

OBJECTIVES

This study aimed to compare the CPT measurement and the cowhage test for sensitive skin and to investigate the correlation between CPT values and cowhage-itch scores.

METHODS

Participants with and without sensitive skin (n = 30, 30) were included. The cowhage test and CPT measurement with its related sensations were performed.

RESULTS

No difference was found in CPT between the sensitive and nonsensitive groups at either the site of the face or the forearm (5, 250, or 2000 Hz). Once the CPT was reached, sensations (itch, stinging, and throbbing) were significantly different between the two groups. Cowhage provoked more intense itch with a longer duration in the face (visual analog scale [VAS] score 1.90 ± 1.47 vs. 0.52 ± 0.90, p < 0.001; duration 3.80 ± 3.31 vs. 0.87 ± 1.43 min, p < 0.001) and forearm (VAS 2.53 ± 2.60 vs. 0.72 ± 1.06, p < 0.001; duration 3.37 ± 3.46 vs. 1.33 ± 2.14 min, p < 0.01) of the sensitive group compared with the nonsensitive group. Cowhage-induced itch and CPT-related itch (5 Hz) showed moderate correlations in both the face (r = 0.441, p < 0.001) and forearm (r = 0.491 p < 0.001) and weak correlations in the forearm (r = 0.323 at 250 Hz, p = 0.012; r = 0.376 at 2000 Hz, p = 0.003).

CONCLUSIONS

Cowhage test showed better performance in assessing the neural sensitivity of sensitive skin in comparison with the CPT measurement. Evaluation of CPT-related sensations may add valuable information to sensitive skin assessment.

Clinical studies in Chinese subjects investigating the tolerance and soothing efficacy of a cream and balm containing 4-t-butylcyclohexanol on the sensitivity of facial skin

INTRODUCTION

Asian subjects are particularly prone to skin sensitivity. We developed a facial cream and balm containing 4-t-butylcyclohexanol to provide skin comfort and a soothing effect for sensitive skin.

OBJECTIVES

Assess the dermatological and ophthalmological tolerance and efficacy in improving skin sensitivity of face cream and balm under normal conditions of use by a population known to be particularly prone to this problem.

METHODS

In a monocentric non-randomized open trial, the cream or balm was applied twice daily to the face, neck, and eye contour of 33 stinger subjects with hypersensitive skin (22-63 years old). Assessments included dermatological and ophthalmological physical and functional signs on Day 1 (D1), D8, and D22, and cosmetic acceptability, cutaneous sensitivity according to a stinging test and the sensitive scale, and the soothing efficacy according to a questionnaire on D22.

RESULTS

The cream and balm were very well tolerated. Immediately after application, subjects reported a reduction in the skin's hypersensitivity (93.9% of subjects for the cream and 81.8% for the balm), skin redness (90.9% of subjects for the cream and 87.9% for the balm), sensations of tightness (93.9% for the cream and 97.0% for the balm), and discomfort sensations (93.9% for the cream and 87.9% for the balm). After 21 days, the application of the cream and balm decreased the stinging scores by 65% and 41%, respectively, with 94% and 77% of subjects showing an improvement, respectively. The sensitivity scale questionnaire indicated that the cream and balm significantly and profoundly decreased all negative signs, for example, irritability, stinging, general discomfort, redness, and dryness on D22 compared to D1. On D22, all 15 parameters recorded were improved by 89%-100% by the cream and by 74%-100% by the balm. The majority (90.9% and 96.8% of subjects using the cream and balm, respectively) of the subjects noticed positive changes in their skin condition after using the product for 21 days.

CONCLUSIONS

The cream and balm were very well-tolerated. This study demonstrated that both products controlled and markedly reduced skin hypersensitivity in Asian subjects, with an immediate and lasting skin soothing and repairing effect over 21 days.

The Challenges in Investigating the Pathogenesis of Sensitive Skin by Noninvasive Measurements: A Systematic Review

Sensitive skin (SS) is a common cutaneous condition that seriously affects people's quality of life, but studies of sensitive skin pathogenesis are unclear, the exploration are ongoing, and the biophysical properties of sensitive skin disagree with the study results. In this paper, we summarize the noninvasive biophysical and imaging instrumental methods used for sensitive skin and provide support for the classification of sensitive skin subtypes to prescribe precise treatment. PubMed and Web of Science databases were searched according to PRISMA guidelines for articles from January 1971 to May 2022 that used noninvasive biophysical or imaging methods to monitor adult subjects with sensitive skin. The quality of the included articles was determined based on 22 items of the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement. A total of 55 studies were included, representing 8 biophysical and 5 imaging methods and their applications in treatment efficacy evaluation studies. The biophysical parameter and cutaneous morphological property changes in sensitive skin subjects were observed. The quality of the studies was relatively low, and there was high variability in results between studies. Several parameters have shown tremendous potential in exploring the pathogenesis with different sensitive skin subtypes: type I may be detected with higher transepidermal water loss and lower stratum corneum hydration values, as well as with thinner epidermis with a shallower and more irregular honeycomb structure; Type II and III are more prone to higher blood flow, lower current perception threshold than normal skin. This systematic review identifies key reasons for the lack of uniform trends in noninvasive measurements and recommends the use of effective selection instruments or relevant parameters to explore the pathogenesis of sensitive skin, and to differentiate the subtypes of sensitive skin for achieving the precise treatment.

Clinical evaluation of anaesthetic-like effect of two dermocosmetic formulations containing Aquaphilus dolomiae extract-G3 in subjects with sensitive facial skin

BACKGROUND

Sensitive skin is a common condition of hyper-reactivity to external stimuli, e.g. heat or abrasion. The symptoms are subjective but can be measured using validated emotional and technical methods. Avène water has several beneficial effects on the skin. In vitro studies indicated that the active component of this natural spring water, Aquaphilus dolomiae extract-G3 (ADE-G3), modulates cutaneous sensitivity via an anaesthetic-like mechanism.

OBJECTIVES

To assess facial skin reactivity after repeated application of two formulations containing ADE-G3.

METHODS

In open-label studies, healthy subjects with sensitive facial skin applied cream or balm twice daily for 84 days. The severity of skin sensitivity was measured using the Sensitive Scale (based on quantifying visible or subjective signs). Subjective responses associated with pain or uncomfortable feeling were assessed by measuring electrodermal response (EDR). This involves measuring variations in skin electrical resistance due to non-conscious physiological changes in activity of the sympathetic nervous system. Subjects were also evaluated for beneficial effects according to a quantitative approach using semantic assessment of a question regarding their skin quality. Evaluations were performed before and after the first application, and after 29/30, 56 and 84 days of twice daily use.

RESULTS

There was a significant decrease in the EDR after stimuli immediately after the application of both ADE-G3 formulations, which continued to decrease over 84 days (40-50% decrease by D85). Likewise, all physical and functional signs of the Sensitive Scale were significantly decreased immediately after the first application and at all time points tested after treatment. Verbatim analysis revealed a semantic shift, from mainly negative terms on D1 to mainly positive terms at D85 for both tested products.

CONCLUSIONS

These results demonstrated that two formulations containing ADE-G3 reduced skin sensitivity, indicating a decreased activation of the sympathetic nervous system associated with this condition.

Can Performance and Gentleness Be Reconciled? A Skin Care Approach for Sensitive Skin

People with self-reported sensitive skin may reluctantly use performing anti-ageing skin care products as it could elicit skin discomfort. We thus aimed to design and test an anti-ageing skin care routine that is suitable for people reporting sensitive skin. Key principles for developing products for sensitive skin were applied and formulas were screened for their mildness in vitro using the Reconstructed Human Epidermis ET50 method. Anti-ageing efficacy and mildness was evaluated during a clinical study in China, with 33 female volunteers aged 40–65 years, with sensitive skin. The anti-ageing benefits were measured using Primos 3D, the cutometer and clinical evaluation. Hallmarks for sensitive skin such as skin hydration, skin barrier, skin redness and response to lactic acid were also measured. The ET50 method yielded values suggesting moderate to mild expected irritancy effect in vivo for most of them, and non-irritating effect for the serum. During the clinical study, no physical or functional signs of discomfort were reported with twice-daily usage of the routine. Instrumental evaluation of Wrinkle depth, skin elasticity/firmness, skin hydration, skin barrier and skin redness revealed improvement at 4 and 8 weeks. Clinical evaluation evidenced skin smoothness, skin suppleness and radiance improvements. The skin was less reactive to lactic acid stimuli, while the sensitive skin burden was lowered according to the dermatological quality of life index. Lastly, a separate investigation suggested the potential relief aspect of such routines to alleviate discomforts from mask wearing. With the right formulation design, the benefits of layering products from a routine can be made accessible to people with sensitive skin while simultaneously alleviating the burden of sensitive skin.

Burden of Sensitive Skin (BoSS) Questionnaire and Current Perception Threshold: Use as Diagnostic Tools for Sensitive Skin Syndrome

The assessment of sensitive skin syndrome, characterized by subjective unpleasant sensations, remains a challenge, since there is no international consensus on the best diagnostic tools. This study evaluated the combination of the Burden of Sensitive Skin (BoSS) questionnaire and the current perception threshold as diagnostic tools for sensitive skin syndrome, and the relationship between BoSS and the subjects’ smoking status, phototype and skin type. A total of 100 women completed the BoSS questionnaire, and current perception threshold was measured on the face. The BoSS score was significantly higher in the self-reported sensitive skin group compared with the non-sensitive skin group (25.61 vs 14.05; p < 0.001), and in non-smokers vs smokers (23.00 vs 18.37; p < 0.05). In addition, the current perception threshold values were similar between the sensitive and non-sensitive groups. These results suggest that BoSS is a better diagnostic tool for sensitive skin syndrome than the current perception threshold, and that smokers less frequently have sensitive skin than do non-smokers.

A new tool to test active ingredient using lactic acid in vitro, a help to understand cellular mechanism involved in stinging test: An example using a bacterial polysaccharide (Fucogel® )

The stinging test is an in vivo protocol that evaluates sensitive skin using lactic acid (LA). A soothing sensation of cosmetics or ingredients can be also appreciated through a decrease in stinging score. To predict the soothing sensation of a product before in vivo testing, we developed a model based on an LA test and substance P (SP) release using a co-culture of human keratinocytes and NGF-differentiated PC12 cells. A bacterial fucose-rich polysaccharide present in Fucogel^® was evaluated as the soothing molecule in the in vivo stinging test and our in vitro model. Excluding toxic concentrations, the release of SP was significant from 0.2% of lactic acid for the PC12 cells and from 0.1% of lactic acid for the keratinocytes. When the pH was adjusted to approximately 7.4, LA did not provoke SP release. At these concentrations of LA, 0.1% of polysaccharide showed a significant decrease in SP release from the two cellular types and in co-cultures without modifying the pH of the medium. In vivo, a stinging test using the polysaccharide showed a 30% decrease in prickling intensity vs the placebo in 19 women between the ages of 21 and 69. Our in vitro model is ethically interesting and is adapted for cosmetic ingredients screening because it does not use animal experimentation and limits human volunteers. Moreover, Fucogel^® reduced prickling sensation as revealed by the in vivo stinging test and inhibits the neurogenic inflammation as showed by our new in vitro stinging test based on SP release.

Reflectance confocal microscopy for the evaluation of sensitive skin

BACKGROUND

Nowadays, the diagnosis for sensitive skin relies on subjective assessment or on the combination of subjective and objective evaluation. No quantitative evaluation is available. It could be expected that confocal microscopy imaging could be of interest to better define the condition.

METHODS

Total 166 healthy female subjects were recruited in this study. Firstly, all subjects completed the sensitive questionnaire. Then, the cutaneous structures were measured by the reflectance confocal microscopy (RCM) on the face and fossa cubitalia. The lactic acid sting test was conducted finally. According to the results of self-perception sensitive skin questionnaire and lactic acid stinging test to evaluate facial skin sensitivity the both positive subjects were regarded as sensitive skin group and both negative group as healthy control group.

RESULT

The results of RCM indicating that the proportion of 'disarranged honeycomb pattern' and 'spongiform edema' in the sensitive group and healthy control group were statistically different (P < 0.05), respectively; The following report 'damaged dermal papilla rings' was not a distinctive pattern, with no significant statistical difference (P > 0.05). The epidermal thickness was 38.88 ± 6.81 μm, healthy control group was 40.31 ± 9.37 μm in, respectively, sensitive skin group and healthy control group, there was no significant statistical difference between the two groups (P > 0.05). The honeycomb structure depth of sensitive group was 20.57 ± 4.86 μm. It was for 23.27 ± 6.38 μm, healthy control group the difference being statistically different between the two groups (P < 0.05).

CONCLUSION

Based on the RCM results, 'epidermal honeycomb structure' and 'spongiform edema' may be used as new skin signs of RCM evaluation of sensitive skin effectively. Indeed, sensitive skin honeycomb structure depth was thinner compared with healthy control group. Such a specific pattern has good clinical and monitoring value for the further exploration. RCM could provide new data and patterns for the evaluation of sensitive skin.

Sensitive skin

Sensitive skin is a clinical condition defined by the self-reported facial presence of different sensory perceptions, including tightness, stinging, burning, tingling, pain and pruritus. Sensitive skin may occur in individuals with normal skin, with skin barrier disturbance, or as a part of the symptoms associated with facial dermatoses such as rosacea, atopic dermatitis and psoriasis. Although experimental studies are still pending, the symptoms of sensitive skin suggest the involvement of cutaneous nerve fibres and neuronal, as well as epidermal, thermochannels. Many individuals with sensitive skin report worsening symptoms due to environmental factors. It is thought that this might be attributed to the thermochannel TRPV1, as it typically responds to exogenous, endogenous, physical and chemical stimuli. Barrier disruptions and immune mechanisms may also be involved. This review summarizes current knowledge on the epidemiology, potential mechanisms, clinics and therapy of sensitive skin.