Racial differences in sodium lauryl sulphate induced cutaneous irritation: black and white

Race, pigmentation, and the human skin barrier-considerations for dermal absorption studies

A functional human skin barrier is critical in limiting harmful exposure to environmental agents and regulating the absorption of intentionally applied topical drug and cosmetic products. Inherent differences in the skin barrier between consumers due to extrinsic and intrinsic factors are an important consideration in the safety assessment of dermatological products. Race is a concept often used to describe a group of people who share distinct physical characteristics. The observed predisposition of specific racial groups to certain skin pathologies highlights the potential differences in skin physiology between these groups. In the context of the human skin barrier, however, the current data correlating function to race often conflict, likely as a consequence of the range of experimental approaches and controls used in the existing works. To date, a variety of methods have been developed for evaluating compound permeation through the human skin, both in vivo and in vitro. Additionally, great strides have been made in the development of reconstructed human pigmented skin models, with the flexibility to incorporate melanocytes from donors of different race and pigmentation levels. Together, the advances in the production of reconstructed human skin models and the increased adoption of in vitro methodologies show potential to aid in the standardization of dermal absorption studies for discerning racial- and skin pigmentation-dependent differences in the human skin barrier. This review analyzes the existing data on skin permeation, focusing on its interaction with race and skin pigmentation, and highlights the tools and research opportunities to better represent the diversity of the human populations in dermal absorption assessments.

Irritant Contact Dermatitis — a Review

Purpose of Review

Recent Findings

Summary

Did human evolution in skin of color enhance the TEWL barrier?

United States will soon be a nation of color; however, much of our knowledge of normal skin disease, and treatment thereof is based on white skin. We and others have attempted to elucidate any potential differences and advantages/disadvantages in skin function that have emerged during homo sapiens evolution post major migration from Eastern Africa. We investigated differences in one stratum corneum function by examining transepidermal water loss (TEWL) measurements in skin of color compared to Caucasian skin. TEWL, a measure of insensible water loss through stratum corneum, plays a major role in human survival. A comprehensive literature search was conducted to procure relevant papers that measured baseline TEWL in skin of color and Caucasian skin. The data show wide contradiction in results for all skin of color groups and white skin and, therefore, no conclusion can be made based on this question. We suggest this variation may be due to experimental confounding variables that impact TEWL quantification, such as anatomic site and sample size subject to further analysis and focus.

Understanding the Sensitive Skin Subject to Achieve a More Holistic Diagnosis

Sensitive skin Syndrome (SSS) is a complex global clinical phenomenon that is defined by the self-reported presence of different sensory perceptions, including tightness, stinging, burning, tingling, pain and pruritus and often without objective signs. Due to the subjective nature of this clinical condition, the diagnosis is complex and there is often a disconnect between what subjects feel and what medical professionals can observe. This chapter reviews the known underlying physiology, some of the triggering factors associated with SSS, co-morbidities as well as the psychological impact on individuals suffering from this condition. The goal is to bridge the gap between the physicians’ understanding and the subjects’ perceptions of this real-life condition that affects so many.

Influence of Ethnicities and Skin Color Variations in Different Populations: A Review

BACKGROUND

In the world scientific tradition, skin color is the primary physical characteristic used to divide humans into groups. Human skin has a wide range of tones and colors, which can be seen in a wide range of demographic populations. Many factors influence the color of people's skin, but the pigment melanin is by far the most important. Melanin is produced by cells called melanocytes in the skin and is the primary determinant of skin color in people with darker skin. Indeed, >150 genes have now been identified as having a direct or indirect effect on skin color. Vitamin D has recently been discovered to regulate cellular proliferation and differentiation in a variety of tissues, including the skin. The mechanisms through which the active vitamin D metabolite 1,25 dihydroxyvitamin D3 (or calcitriol) affects keratinocyte development are numerous and overlap with the mechanisms by which calcium influences keratinocyte differentiation. Ultraviolet (UV) is the most major modifiable risk factor for skin cancer and many other environmental-influenced skin disorders when it is abundant in the environment. Although the UV component of sunlight is known to cause skin damage, few researches have looked at the impact of non-UV solar radiation on skin physiology in terms of inflammation, and there is less information on the role of visible light in pigmentation.

SUMMARY

The quantity and quality of melanin are regulating by the expression of genes. The enzyme tyrosinase is primarily responsible for the genetic mechanism that controls human skin color. Genetics determines constitutive skin color, which is reinforced by facultative melanogenesis and tanning reactions. High quantities of melanin and melanogenic substances are typically accepted in darker skin to protect against UV radiation-induced molecular damage. Previous research has proposed that skin color variation is caused by a dynamic genetic mechanism, contributing to our understanding of how population demographic history and natural selection shape human genetic and phenotypic diversity. However, the most significant ethnic skin color difference is determined by melanin content. This current review aimed to assess the influence of skin color variations in skin structure and functions as well as difference in dermatological disease patterns. Also, this article reviewed several cases of skin color adaptation in different populations. Key Messages: Skin color impacts the composition and activity. Therefore, the contrast of dermatological ailments between distinct race-related categories is remarkable. Skin color adaptation is a challenging procedure. Refinement of skin color is an age-old craving of humans with ever-evolving drifts.

Oral Hyaluronan Relieves Wrinkles and Improves Dry Skin: A 12-Week Double-Blinded, Placebo-Controlled Study

Hyaluronan (HA) is present in all connective tissues and organs, including the skin and joint fluid. However, few clinical trials have comprehensively evaluated the impacts of oral HA on skin conditions, including wrinkles and moisturization. In this study, we conducted a placebo-controlled, randomized, double-blind trial of daily HA (120 mg) intake for 12 weeks in 40 healthy Asian men and women (aged 35-64 years). Skin condition was determined by the evaluation of wrinkles, stratum corneum water content, the amount of transepidermal water loss, elasticity, and through image analysis. After 12 weeks, skin condition was significantly improved in terms of wrinkle assessment, stratum corneum water content, transepidermal water loss, and elasticity in the HA group compared to the placebo group. Regarding the percentage change from baseline, wrinkle assessment, stratum corneum water content, and skin elasticity were significantly improved in the HA group versus the placebo group after 8 and 12 weeks of ingestion. The present findings indicate that oral ingestion of HA may suppress wrinkles and improve skin condition.

Twenty Clinically Pertinent Factors/Observations for Percutaneous Absorption in Humans

At least 20 clinically relevant factors affect percutaneous absorption of drugs and chemicals: relevant physico-chemical properties, vehicle/formulation, drug exposure conditions (dose, duration, surface area, exposure frequency), skin appendages (hair follicles, glands) as sub-anatomical pathways, skin application sites (regional variation in penetration), population variability (premature, infants, and aged), skin surface conditions (hydration, temperature, pH), skin health and integrity (trauma, skin diseases), substantivity and binding to different skin components, systemic distribution and systemic toxicity, stratum corneum exfoliation, washing-off and washing-in, rubbing/massaging, transfer to others (human to human and hard surface to human), volatility, metabolic biotransformation/cutaneous metabolism, photochemical transformation and photosensitivity, excretion pharmacokinetics, lateral spread, and chemical method of determining percutaneous absorption.

Chromametric assessment of drug skin tolerance: A comparative study between Africans and Caucasians skins

BACKGROUND/AIMS

During dermatological forms development, one of the simplest non-invasive techniques used to evaluate cutaneous tolerance of formulations is to monitor the color changes using a tristimulus chromameter. Most published tolerance studies involving chromametric measurements are performed on Caucasian subjects. However, in the context of drug formulation for African-type populations, it is not always relevant to transpose tolerance results obtained on Caucasians populations to African-type ones due to histological ethnic differences of the skin. The goal of this work was to assess whether tristimulus chromameter can be used to highlight color variations following the application of dermatological topics on black skin in order to validate skin tolerance studies made on African-type subjects.

MATERIALS AND METHODS

After application of two commercial creams with opposite side effects (skin irritation and skin blanching) in both Africans and Caucasians populations, color variations were evaluated using a tristimulus chromameter in L^* a^* b^* color system and compared between both populations. L^* indicating color brightness, a^* represents green and red directions and b^* represents blue and yellow directions.

RESULTS

While skin irritation resulted in a significant increase of a^* parameter in both studied populations, the skin blanching resulted in a decrease of a^* associated with an increase of L^* .

CONCLUSION

We established that tristimulus chromameter can be used to achieve in vivo skin tolerance study of dermatologic formulations in Africans despite their dark skin even though it appeared less sensitive. This study can speed up the development of dermatological forms dedicated to Africans and/or Caucasians subjects.

The Prevalence of Sensitive Skin

Sensitive skin has been described as unpleasant sensory responses to stimuli that should not provoke such sensations. Objectively measurable signs of irritation are not always present in individuals with sensitive skin, however, subjective sensory effects such as, itching, burning, stinging, tightness, and dryness, are consistently present. Given the subjective nature of the phenomenon known as sensitive skin, surveys have been a popular approach to evaluating the prevalence of this condition among the general population, and a number of them have been conducted worldwide. Overall, ~60–70% of women and 50–60% of men report having some degree of sensitive skin. However, there are differences between populations in various geographies, and perceptions of sensitive skin at specific anatomic sites. This article is a review of survey data on the prevalence of self-declared sensitive skin in various geographies, among different gender and age groups, and at various anatomic sites. In addition, we review the factors that may contribute to sensitive skin, and the physiological characteristics associated with this condition, including impaired barrier function and heightened neural reactions.

Effect of Mild Hyperthermia on Transdermal Absorption of Nicotine from Patches

Application of heat (hyperthermic conditions) on skin is known to enhance drug transfer and facilitate skin penetration of molecules. The aim of this work was to study the effect of hyperthermia on the drug release and skin permeation from nicotine transdermal patches. The drug release and skin permeation were characterized by in vitro release test and in vitro permeation test. The temperature was maintained at 32 °C as control (simulating normal physiological skin temperature) and 42 °C as hyperthermia condition. The in vitro release test was carried out using USP apparatus 5-Paddle over disk method for a transdermal patch. Skin permeation study was carried out across porcine skin using the flow through cells (PermeGear, Inc.) with an active diffusion area of 0.94 cm². Mechanistic studies (parameters such as partition coefficient, TEWL and electrical resistivity) were also performed to understand the mechanisms involved in determining the influence of hyperthermia on drug delivery from transdermal patches of nicotine. The rate and extent of drug release from nicotine patch was not significantly different at two temperatures (Cumulative release after 12 h was 43.99 ± 3.29% at 32 °C and 53.70 ± 5.14% at 42 °C). Whereas, in case of in vitro permeation studies, the nicotine transdermal permeation flux for patch was threefold higher at 42 °C (100.1 ± 14.83 μg/cm²/h) than at 32 °C (33.3 ± 14.83 μg/cm²/h). The mechanistic studies revealed that the predominant mechanism of enhancement of drug permeation by hyperthermia condition is by the way of increasing the skin permeability. There is a potential concern of dumping of higher dose of nicotine via transdermal route.

Transepidermal water loss, stratum corneum hydration, and skin surface pH of female African and Caucasian nursing students

BACKGROUND

Conflicting evidence exists on how skin barrier function compares between Africans and Caucasians. This study measured skin barrier function of South African first year nursing students before their practical training started to compare skin barrier function between the racial groups.

METHODS

Transepidermal water loss (TEWL), stratum corneum (SC) hydration, and skin surface (SS) pH was measured on female first year nursing students (19 African and 31 Caucasian; age range 18-40 years). Geometric means and ranges were calculated and the influence of anatomical areas and racial differences were evaluated respectively.

RESULTS

No significant difference in TEWL was established between the racial groups. SC hydration was significantly lower (P ≤ 0.05) and SS-pH was significantly higher (P ≤ 0.0001) in African nursing students when compared to Caucasians. African nursing students had significantly lower (P ≤ 0.05) SC hydration on their palms when compared to the other anatomical areas.

CONCLUSION

Stratum corneum hydration and SS-pH differed significantly between African and Caucasian skin, while no difference was found for TEWL, the primary parameter used to evaluate skin barrier function. Low SC hydration and high SS-pH of African nursing students prior to their practical training, may suggest a higher risk for developing occupational skin diseases.

Dermatotoxicology of sulfur mustard: Historical perspectives from World War I

Sulfur mustard has been used as a chemical warfare agent for the past century. After its introduction by the Germans in World War I, investigators quickly began studying its impact on the human body including its deleterious effects on skin. This review focuses on two groups in particular who conducted experiments from 1917 to 1918: the United States Army at the American University Experiment Station Laboratories and Torald Sollmann at Western Reserve University. Through this work, these researchers proved far ahead of their time by anticipating dermatologic phenomena not described in the literature until later in the twentieth century. These include regional variation of percutaneous penetration, effect of vehicle on penetration and predicting immunologic contact urticaria. The work conducted by these researchers set the groundwork for much of twentieth century dermatotoxicology.

Evaporative Water Loss in Superficial to Full Thickness Burns

INTRODUCTION

Increased evaporative water loss (EWL) in burn patients leads to dehydration and hypothermia. Early clinical studies performed with outdated hygrometers suggested a 17 to 75 times increased EWL in burns with contradicting results for the different burn depths.Our study proposals were: (1) obtain reliable data of the EWL of all burn depths, (2) compare these results with findings from earlier studies, (3) evaluate the usefulness of the EWL in differentiating between superficial and deep partial thickness burns, (4) determine the effect of Biobrane on the EWL of superficial partial thickness burns in vivo, and (5) evaluate the effect of the sterile incision foil Opraflex on the EWL in split skin graft donor sites.

METHODS

We measured the EWL of all burn depths in 28 patients under stable and recorded conditions regarding room temperature and humidity with a modern digital evaporimeter (Tewameter TM 300). For the first time in vivo, we also determined the effect of Biobrane on the EWL of burns and evaluated the EWL in split skin graft donor sites covered with Opraflex.

RESULTS

The EWL in all burn depths was significantly increased (P < 0.001) compared with unburned skin. There was no significant difference (P > 0.05) in the EWL of superficial compared with deep partial thickness burns, whereas full thickness burns had a significantly lower EWL (P < 0.05) compared with superficial and deep partial thickness burns. Biobrane significantly reduced the EWL (P < 0.05) of superficial partial thickness burns. The EWL of Opraflex covered skin graft donor sites was significantly reduced compared with uncovered donor sites (P < 0.05).

CONCLUSIONS

Our data suggest that the actual EWL in burns is approximately 3 times higher in full thickness burns and approximately 4 times higher in superficial and deep partial thickness burns compared with normal skin and therefore much lower than suggested previously.Because there was no significant difference in the EWL of superficial compared with deep partial thickness burns, the EWL cannot be used to differentiate between these burn depths.Biosynthetic wound dressings can significantly reduce the EWL of superficial partial thickness burns and sterile incision foil protects split skin graft donor sites from an increased EWL.

Temporal and Racial Differences Associated with Atopic Dermatitis Staphylococcusaureus and Encoded Virulence Factors

Monitoring pathogen emergence provides insight into how pathogens adapt in the human population. Secreted virulence factors, important contributors to infections, may differ in a manner dependent on the strain and host. Temporal changes of Staphylococcus aureus toxigenic potential, for example, in encoding toxic shock syndrome toxin 1 (TSST-1), contributed to an epidemic of TSS with significant health impact. This study monitored changes in atopic dermatitis (AD) S. aureus isolates and demonstrated both temporal and host infection differences according to host race based on secreted superantigen potential. The current temporal increase in enterotoxin gene cluster superantigen prevalence and lack of the gene encoding TSST-1 in AAs predict differences in infection types and presentations.

Atopic dermatitis (AD) is an inflammatory skin condition strongly associated with Staphylococcus aureus colonization and infection. S. aureus strains shift in populations in ~10-year intervals depending on virulence factors. Shifts in S. aureus virulence factors may in part explain the racial differences observed in the levels of prevalence and severity of AD. AD S. aureus isolates collected from 2011 to 2014 (103 isolates) and in 2008 (100 isolates) were examined for the prevalence of genes encoding superantigens (SAgs). The strains from 2011 to 2014 were obtained from AD patients as a part of the National Institute of Allergy and Infectious Diseases (NIAID) Atopic Dermatitis Research Network (ADRN). The prevalence of SAg genes was investigated temporally and racially. The enterotoxin gene cluster (EGC) was more prevalent in the 2011–2014 AD isolates than in the 2008 AD isolates. The prevalences of virulence factor genes were similar in European American (EA) and Mexican American (MA) patients but differed in 6 of 22 SAg genes between EA and African American (AA) or MA and AA isolates; notably, AA isolates lacked tstH, the gene encoding toxic shock syndrome toxin 1 (TSST-1). The presence of tstH and sel-p (enterotoxin-like P) was associated with decreased clinical severity and increased blood eosinophils, respectively. The EGC is becoming more prevalent, consistent with the previously observed 10 years of cycling of S. aureus strains. Race-specific S. aureus selection may account for differences in virulence factor profiles. The lack of TSST-1-positive (TSST-1⁺) AD S. aureus in AA is consistent with the lack of AAs acquiring TSST-1-associated menstrual toxic shock syndrome (TSS).

IMPORTANCE Monitoring pathogen emergence provides insight into how pathogens adapt in the human population. Secreted virulence factors, important contributors to infections, may differ in a manner dependent on the strain and host. Temporal changes of Staphylococcus aureus toxigenic potential, for example, in encoding toxic shock syndrome toxin 1 (TSST-1), contributed to an epidemic of TSS with significant health impact. This study monitored changes in atopic dermatitis (AD) S. aureus isolates and demonstrated both temporal and host infection differences according to host race based on secreted superantigen potential. The current temporal increase in enterotoxin gene cluster superantigen prevalence and lack of the gene encoding TSST-1 in AAs predict differences in infection types and presentations.

Assessment of the variation of skin barrier function with anatomic site, age, gender and ethnicity

The skin is the largest organ of the human body and its functions include protection, thermoregulation sensation and secretion. Significant advances in our understanding of how the morphology and physiology of the skin contribute to the skin's barrier role have been achieved in recent years. The aim of this review is to summarize the principal approaches which have been used to assess variation in skin barrier function with anatomic site, age, gender, and ethnicity. The methods discussed include trans-epidermal water loss (TEWL) measurement, assessment of corneocyte size, response to vasoactive compounds and attenuated total reflectance Fourier transform infrared (ATR-FTIR) interrogation of skin. The utility of the various methods is considered and the most important findings in the literature to date are highlighted.

Analysis of blood and lymph vascularization patterns in tissue-engineered human dermo-epidermal skin analogs of different pigmentation

PURPOSE

Bioengineered dermo-epidermal skin analogs containing melanocytes represent a promising approach to cover large skin defects including restoration of the patient's own skin color. So far, little is known about the development of blood and lymphatic vessels in pigmented skin analogs after transplantation. In this experimental study, we analyzed the advancement and differences of host blood and lymphatic vessel ingrowth into light- and dark-pigmented human tissue-engineered skin analogs in a rat model.

METHODS

Keratinocytes, melanocytes, and fibroblasts from light- and dark-pigmented skin biopsies were isolated, cultured, and expanded. For each donor, melanocytes and keratinocytes were seeded in ratios of 1:1, 1:5, and 1:10 onto fibroblast-containing collagen gels. The skin analogs were subsequently transplanted onto full-thickness wounds of immuno-incompetent rats and quantitatively analyzed for vascular and lymphatic vessel density after 8 and 15 weeks.

RESULTS

The skin analogs revealed a significant difference in vascularization patterns between light- and dark-pigmented constructs after 8 weeks, with a higher amount of blood vessels in light compared to dark skin. In contrast, no obvious difference could be detected within the light- and dark-pigmented group when varying melanocyte/keratinocyte ratios were used. However, after 15 weeks, the aforementioned difference in blood vessel density between light and dark constructs could no longer be detected. Regarding lymphatic vessels, light and dark analogs showed similar vessel density after 8 and 15 weeks, while there were generally less lymphatic than blood vessels.

CONCLUSION

These data suggest that, at least during early skin maturation, keratinocytes, melanocytes, and fibroblasts from different skin color types used to construct pigmented dermo-epidermal skin analogs have distinct influences on the host tissue after transplantation. We speculate that different VEGF expression patterns might be involved in this disparate revascularization pattern observed.

International guidelines for the in vivo assessment of skin properties in non-clinical settings: Part 2. transepidermal water loss and skin hydration

BACKGROUND

There is an emerging perspective that it is not sufficient to just assess skin exposure to physical and chemical stressors in workplaces, but that it is also important to assess the condition, i.e. skin barrier function of the exposed skin at the time of exposure. The workplace environment, representing a non-clinical environment, can be highly variable and difficult to control, thereby presenting unique measurement challenges not typically encountered in clinical settings.

METHODS

An expert working group convened a workshop as part of the 5th International Conference on Occupational and Environmental Exposure of Skin to Chemicals (OEESC) to develop basic guidelines and best practices (based on existing clinical guidelines, published data, and own experiences) for the in vivo measurement of transepidermal water loss (TEWL) and skin hydration in non-clinical settings with specific reference to the workplace as a worst-case scenario.

RESULTS

Key elements of these guidelines are: (i) to minimize or recognize, to the extent feasible, the influences of relevant endogenous-, exogenous-, environmental- and measurement/instrumentation-related factors; (ii) to measure TEWL with a closed-chamber type instrument; (iii) report results as a difference or percent change (rather than absolute values); and (iv) accurately report any notable deviations from this guidelines.

CONCLUSION

It is anticipated that these guidelines will promote consistent data reporting, which will facilitate inter-comparison of study results.

Optimal patch application time in the evaluation of skin irritation

We investigated the optimum application for evaluating skin irritation response by using samples of irritants commonly used as additives in cosmetics and other common household products. We studied 47 volunteers (16 men and 31 women). We selected three types of surfactant, one moisturizer, one anti-infective agent and one oil solution. Using Finn chambers on Scanpor tape, we performed the patch test. A total of 0.015 mL of each sample was applied to the Finn chamber. For liquids, circular filter paper was soaked in 0.015 mL of the sample. Samples were placed on the upper back of participants, and closed for 4, 24 or 48 h. A patch application time of 24 h is sufficient to detect primary skin irritation from irritants in cosmetics and other common household products. In addition, we found that skin irritation reactions were strongest at 24 h after patch removal and that the reaction tended to be weaker at 48 h after patch removal. Patch testing to evaluate irritants should be performed by means of a 24-h patch test with a follow-up reading at 24 h after patch removal. An application time of 24 h places less of a burden on patients than a 48-h patch test.

Influence of skin type, race, sex, and anatomic location on epidermal barrier function

The intact skin represents a barrier to the uncontrolled loss of water, proteins, and plasma components from the organism. Owing to its complex structure, the epidermal barrier with its major layer, the stratum corneum, is the rate-limiting unit for the penetration of exogenous substances through the skin. The epidermal barrier is not a static structure. The status of different functions of the epidermis can be monitored by assessing specific biophysical parameters such as transepidermal water loss, stratum corneum hydration, and skin surface pH. Variables originating from the individual as well as exogenous factors have an important influence on the epidermal barrier parameters.

Epidermal permeability barrier recovery is delayed in vitiligo-involved sites

BACKGROUND/OBJECTIVES

Prior studies have demonstrated that both the skin surface pH and epidermal permeability barrier function vary with skin pigmentation types. Although melanin deficiency is the main feature of vitiligo, alterations in cutaneous biophysical properties in vitiligo have not yet been well defined. In the present study, stratum corneum (SC) hydration, the skin surface pH and epidermal permeability barrier function in vitiligo were evaluated.

METHODS

A total of 30 volunteers with vitiligo comprising 19 males and 11 females aged 13-51 years (mean age: 27.91 +/- 2.06 years) were enrolled in this study. The skin surface pH, SC hydration, melanin/erythema index and transepidermal water loss (TEWL) were measured by respective probes connected to a Courage-Khazaka MPA5. SC integrity was determined by measuring the TEWL following each D-Squame application. The barrier recovery rate was assessed at 5 h following barrier disruption by repeated tape stripping.

RESULTS

In addition to SC hydration, both melanin and erythema index were significantly lower in vitiligo lesions than in contralateral, nonlesional sites, while no difference in skin surface pH between vitiligo-involved and uninvolved areas was observed. In addition, neither the basal TEWL nor SC integrity in the involved areas differed significantly from that in the uninvolved areas. However, barrier recovery in vitiligo-involved sites was significantly delayed in comparison with uninvolved sites (40.83 +/- 5.39% vs. 58.30 +/- 4.71%; t = 2.441; p < 0.02).

CONCLUSION

Barrier recovery following tape stripping of the SC is delayed in vitiligo. Therefore, improvement in epidermal permeability barrier function may be an important unrecognized factor to be considered in treating patients with vitiligo.

Cutaneous blood flow in dermatomyositis and its association with disease severity

BACKGROUND

Several studies using nailfold capillary microscopes have demonstrated capillary changes in patients with dermatomyositis (DM); however, no previous study has examined cutaneous blood flow in this disease.

PURPOSE

To determine cutaneous blood flow in involved and non-involved skin surfaces of patients with DM and to assess possible correlation with clinical measures of disease severity.

METHODS

Using a Laser Doppler perfusion imager, cutaneous blood flow was measured at six targeted sites of involved and apparently non-involved skin of 13 DM patients and the corresponding non-involved sites of 13 healthy controls. Overall disease severity of DM patients was determined by physician's global assessment (PGA), creatinine phosphokinase (CPK) levels, medical research council (MRC) scores, and the DM skin severity index (DSSI).

RESULTS

Skin blood flow was significantly elevated in involved vs. non-involved skin of DM patients at all anatomic sites measured: periungual (P=0.001), knuckle (P=0.001), elbow (P=0.013), periorbital (P=0.015), chest (P=0.028), and back (P=0.001). Blood flow was also higher in apparently non-involved skin of DM patients vs. skin of healthy controls at all anatomic sites, although statistical significance was not achieved. A significant negative correlation was observed between the DSSI and blood flow in involved skin of the chest (P=0.003), back (P=0.002), and knuckle (P=0.026).

CONCLUSION

DM is associated with significantly increased cutaneous blood flow, even at sites where no erythema is evident. This suggests significant involvement of the skin vasculature in this disease process.

The effect of population diversity on skin irritation

The impact of many human variables on the response to skin irritating substances has been studied to varying degrees, including the impact of age, sex, and atopic status. However, the importance of ethnic origin has been more difficult to investigate, leading to a relative paucity of compelling data, either for or against the existence of differences. A primary reason for this lack is that studies on different ethnic groups often have to be undertaken in different locations thus introducing variables, e.g. time, environmental conditions that confound interpretations. In the present work, an attempt has been made to eliminate all variables except ethnicity by conducting a study on 2 distinct populations (Punjabis and Tamils) at the same location on the same day with a single assessor of the skin reactions, using sodium lauryl sulfate as the skin irritant. The skin reactions were assessed visually, and it was demonstrated that the modality of the reactions in these 2 populations had clear differences, but that the dose-response profiles were very similar. Thus, although the irritant response was expressed differently (e.g. erythema was much less evident in the darker Tamil population), the overall outcome was that the populations reacted in an equivalent manner.

Influence of usage practices, ethnicity and climate on the skin compatibility of sanitary pads

Modern disposable sanitary pads are becoming available worldwide. Regional differences in usage practices, ethnicity, and climate may influence their skin compatibility. Pad usage practices depend on culture, economics, and menstrual physiology. Daily usage is higher in Japan and but lower in Nigeria compared to North America or Western Europe. Evidence for ethnic differences in skin irritant susceptibility is not compelling. Dark skin may be less susceptible to certain irritants than fair skin; the Japanese may experience a higher degree of sensory irritation than Caucasians. Ambient conditions such as high temperature and humidity increase the skin temperature and skin surface moisture under sanitary pads by small but measurable amounts, causing no discernible skin irritation; vapor-permeable pad backings reduce these effects. Cold dry conditions, which can irritate exposed skin, may not affect vulvar skin to the same degree due to its elevated hydration and occlusion. To address the practical significance of these variables, results of prospective clinical trials of sanitary pads performed by industry and academic scientists in North America (Indiana), Mexico, Western Europe (Munich, Athens, Goteborg, Sweden), Eastern Europe (Kiev) and Africa (Abuja, Nigeria) were reviewed. Despite the diverse range of conditions, no significant adverse skin effects were observed with modern pads compared to traditional pad designs. Study participants generally preferred modern pads for performance and comfort.

The combination of 2% 4-hydroxyanisole (mequinol) and 0.01% tretinoin effectively improves the appearance of solar lentigines in ethnic groups

While the efficacy and safety of topical 4-hydroxyanisole (mequinol) 2%/tretinoin 0.01% therapy has been established in Caucasian populations, those with skin types I-II, little research has focused on individuals with darker skin types. The purpose of this open-label study was to evaluate the efficacy and safety of mequinol 2%/tretinoin 0.01% solution in the treatment of solar lentigines in Asian, Latin/Hispanic, and African American ethnic groups with skin types II-V. Subjects were required to have >or= 10 solar lentigines on the dorsal forearms/hands and >or= 3 on the face. One lesion was designated the target lesion, however, all lesions were treated. Patients were treated with topical mequinol 2%/tretinoin 0.01% and clinically evaluated at 4, 8, 12, 16, 20, and 24 weeks as well as 4 weeks following treatment cessation. At each visit, lesions were evaluated using Target and Overall Lesion Pigmentation Index scores ranging from 0 (lightest) to 8 (darkest), where 4 indicated equal pigment with surrounding skin. Efficacy was determined based on pigmentation index scores, and safety was assessed using laboratory monitoring and adverse event (AE) reporting. Over 80% of the 259 subjects completing this study responded to mequinol 2%/tretinoin 0.01% therapy, with a majority of subjects maintaining clinical benefit at 4 weeks post-treatment. Most AEs reported were tolerable and overall mequinol 2%/tretinoin 0.01% therapy had a favorable benefit-to-risk ratio. This study therefore supports the theory that topical mequinol 2%/tretinoin 0.01% is an effective and safe treatment of solar lentigines in ethnic populations, and in those with dark skin types.

Irritant contact dermatitis induced by a common household irritant: A noninvasive evaluation of ethnic variability in skin response

OBJECTIVE

This study was undertaken to investigate the ethnic susceptibility to irritant contact dermatitis induced by a common dishwashing liquid using noninvasive technologies.

METHODS

A total of 30 participants (15 Caucasian, 15 African American) were patch tested to graded concentrations of a common household irritant and evaluated using clinical scoring, reflectance confocal microscopy, transepidermal water loss, and fluorescence excitation spectroscopy.

RESULTS

At 24 hours, the concentration thresholds for clinically perceptible irritancy were significantly higher for African American compared with Caucasian participants. Reflectance confocal microscopy showed stratum corneum disruption, parakeratosis, and spongiosis; these features were more severe in Caucasian participants (P < or = .002). Mean values for transepidermal water loss were significantly higher in the Caucasian group at comparable clinical scores (P < or = .005). Fluorescence excitation spectroscopy showed a broad excitation band at 300 nm (emission 340 nm) and values in both groups returned to baseline by day 7.

LIMITATIONS

This pilot study was limited in scope and larger studies are needed to further evaluate ethnic differences in irritant contact dermatitis and to demonstrate the applicability of our findings for other irritants.

CONCLUSION

Clinical evaluation, reflectance confocal microscopy, and transepidermal water loss showed significant differences in the cutaneous irritant response between both groups suggesting a superior barrier function of African American skin. Fluorescence excitation spectroscopy on the other hand demonstrated no differences in the hyperproliferative response after irritant exposure and indicated similar kinetics for the two groups.

Additive impairment of the barrier function by mechanical irritation, occlusion and sodium lauryl sulphate in vivo

BACKGROUND

The interaction between potential irritants in the workplace might be important because workers are not usually exposed to a single irritant, but to multiple potentially harmful substances. Physical irritant contact dermatitis caused by friction or mechanical abrasion is a common occupational dermatosis. Prolonged water exposure by occlusion is also common in the workplace. Several studies have revealed the negative effect of the common anionic detergent sodium lauryl sulphate (SLS) on permeability barrier function.

OBJECTIVES

To study the additive impairment of permeability barrier function by mechanical irritation combined with 0.5% SLS or prolonged water exposure by occlusion, as models of mild irritation.

METHODS

The volar forearms of 20 healthy volunteers were exposed to mechanical irritation and occlusion with water or 0.5% SLS for four consecutive days in a combined tandem repeated irritation test (TRIT). Permeability barrier function was measured with a Tewameter TM 210. Irritation was assessed with a Chromameter CR 300 and a visual score.

RESULTS

Barrier disruption in our model was rated as follows: occlusion with SLS and mechanical irritation > occlusion with SLS > occlusion with water and mechanical irritation > mechanical irritation and occlusion with water > occlusion with a glove and mechanical irritation > mechanical irritation > occlusion with water. Barrier disruption caused by occlusion or mechanical irritation was enhanced by the tandem application. The choice of irritant under occlusion, time of occlusion and order of tandem application all affected the degree of barrier disruption. Evaporimetry was able to detect early stages in the development of an irritant reaction before it became visible. Chromametry was not able to detect this early response.

CONCLUSIONS

Physical irritants (friction, abrasive grains, occlusion) and detergents such as SLS represent a significant irritation risk and should be minimized, especially when acting together, as shown in our TRIT model.

Effect of occupational exposure to rayon manufacturing chemicals on skin barrier to evaporative water loss

To evaluate the effects of the occupational exposure to rayon manufacturing chemicals (RMC, containing predominantly carbon disulfide (CS(2)) and minor sulfuric acid) in a rayon factory on the basal transepidermal water loss (TEWL), barrier integrity (BI), and sequential increasing TEWL profiles. Six Thais and five Chinese workers in the spinning department of a rayon manufacturing plant and five healthy unexposed controls were recruited as the test subjects. An area of 4.5 x 5.5 cm on the mid-side of the volar forearm on the right hand was stripped by means of moderate pressure with commercially available adhesive tape by the same technician throughout the experiment. The skin was progressively stripped until glistening. TEWL was measured at every three and five tape strips on the right hand. The corresponding site on the left hand was measured parallel as the self-control. We found significant differences in basal TEWL and in BI between Chinese workers and Chinese controls, and between Thai workers and Chinese workers, respectively. Two-stage patterns of progressive TEWL profiles were found in such a chronic and repeated occupational exposure to RMC containing CS(2). The occupational exposure to RMC could result in the perturbation of the skin barrier function. Basal TEWL might be more sensitive to chronic skin irritant exposure. The TEWL profile achieved to the glistening stage might be necessary to avoid erroneous pattern estimation. Due to the lack of Thais control in this study, the racial difference in response to the RMC warrants further study.

Sensitive skin: a complex and multifactorial syndrome

Many people complain of discomfort after application of commonly used skin care products, particularly to the face. This hyperreactivity of the skin is a non-immunologically mediated skin inflammation. It seems to be the result of an intolerance of the skin to various stimuli that are normally well tolerated. It is difficult to assess the prevalence of 'sensitive skin' and sensitive skin-related cosmetic intolerance because of the many possible exogenous and endogenous factors that trigger or aggravate this multifactorial syndrome. A thorough history is essential. Sometimes patch testing is needed both to standard allergens and also to all the patients' cosmetics and skin care products. All cosmetics should be stopped and then reintroduced one by one, at intervals of one to two weeks. The number, type and frequency of the application of skin care products used in the final programme should remain limited. Some patients benefit from psychological or even psychiatric help. Management is usually difficult and all therapeutic measures should be undertaken with patience and tenacity.

Prediction of irritancy in the human skin irritancy model and occupational setting

It is of great importance to find ways to lower the incidence of chronic irritant contact dermatitis. In this process, it is crucial to have insight in the factors that can predict irritancy. This review offers a survey of recent findings in the field of skin irritancy testing, discussed in the context of renowned, older work. Extrinsic and intrinsic factors that may determine the outcome of irritancy testing in the human skin model are considered. In recent decades, there has been increasing interest in factors influencing the development of occupational dermatitis by means of prospective cohort studies. This promising new area of investigation is discussed separately.

Efficacy of dexpanthenol in skin protection against irritation: a double-blind, placebo-controlled study

Dexpanthenol is popular in treating various dermatoses and in skin care, but few controlled clinical trials have been performed. We investigated the efficacy of dexpanthenol in skin protection against irritation in a randomized, prospective, double-blind, placebo-controlled study. 25 healthy volunteers (age 18-45 years) were treated for the inner aspect of both forearms with either Bepanthol Handbalsam containing 5% dexpanthenol or placebo x2 daily for 26 days. From day 15-22, sodium lauryl sulfate (SLS) 2% was applied to these areas x2 daily. Documentation comprised sebumetry, corneometry, pH value and clinical appearance (photographs). 21 volunteers completed the study, 3 were excluded because of non-compliance and 1 experienced a non-study-related, severe, adverse event. Only corneometry yielded a statistically significant difference, with decreased values following SLS challenge at the placebo sites (P < 0.05). Intraindividual comparisons showed superior results at the dexpanthenol-treated sites in 11 cases and in only 1 case at the placebo site. 6 volunteers experienced an irritant contact dermatitis, with more severe symptoms at the placebo site in 5 cases. In conclusion, dexpanthenol exhibits protective effects against skin irritation. The initiation of a study to evaluate the efficacy of dexpanthenol in preventing irritant occupational contact dermatitis under real workplace conditions is validated.

Ethnic skin: overview of structure and function

Racial variability in skin function is an area in which data often conflict. Understanding and quantifying racial differences in skin function are important for skin care and the prevention and treatment of skin diseases. A key feature that characterizes race is skin color: Is deeply pigmented skin different from fair skin in terms of responses to chemical and environmental insults? Is skin care the same? Are there different risks among racial groups of developing a skin disease after exposure to the same insults? The interpretation of pathophysiologic phenomena should consider not only anatomic and functional characteristics of ethnic groups but also socioeconomic, hygienic, and nutritional factors. This article reviews and discusses recent findings.

Confocal histopathology of irritant contact dermatitis in vivo and the impact of skin color (black vs white)

BACKGROUND

The pathogenesis of irritant contact dermatitis and its modulation according to skin color is not well understood. Reflectance confocal microscopy (RCM) enables high-resolution, real-time, in-vivo imaging of human skin.

OBJECTIVE

The goal of our study was to use RCM to determine whether susceptibility to irritant contact dermatitis differs between black and white skin.

METHODS

Participants were placed in groups on the basis of skin color and the volar aspects of their forearms exposed to 1% and 4% sodium lauryl sulfate using Finn Chambers (Allerderm Laboratories Inc, Petaluma, Calif). They were evaluated at 6, 24, and 48 hours by RCM, transepidermal water loss, laser Doppler velocimetry, and routine histology.

RESULTS

Participants with white skin had more severe clinical reactions than those with black skin. RCM revealed microscopic changes even without clinical evidence of irritation. Confocal features included parakeratosis, spongiosis, perivascular inflammatory infiltrate, and microvesicle formation, and these features were confirmed by routine histology. Also, participants with white skin had greater mean increases in transepidermal water loss after exposure to 4% sodium lauryl sulfate than did participants with black skin.

CONCLUSION

In-vivo RCM can track early pathophysiologic events revealing differences between black and white skin during the development of irritant contact dermatitis, and may support the theory that those with black skin are more resistant to irritants.

Racial (ethnic) differences in skin properties: the objective data

Racial (ethnic) differences in skin properties may explain racial disparities seen in dermatologic disorders and provide insight into appropriate differences in the management of these disorders. However, racial differences in skin have been minimally investigated by objective methods and the data are often contradictory. Objective methods studied include transepidermal water loss (TEWL), water content (WC), corneocyte variability, blood vessel reactivity, elastic recovery/extensibility, pH gradient, lipid content, surface microflora, microscopic evaluation of mast cell granules, and confocal microscopy. The majority of the evidence (six out of eight studies) indicates that TEWL is greater in Black skin compared with White skin. TEWL measurements of Asian skin are inconclusive as they have been found to be equal to Black skin and greater than Caucasian skin, equal to Caucasian skin, and less than all other ethnic groups in different studies. Racial differences in WC, as measured by resistance, capacitance, conductance and impedance, are also inconclusive as the data are contradictory. While the evidence regarding corneocyte desquamation is minimal, one clinically provocative observation is that Blacks have a 2.5 times greater spontaneous desquamation rate compared with Caucasians and Asians, possibly accounting for an increased frequency of xerosis seen clinically in Blacks. With regards to blood vessel reactivity, studies can not be compared to each other because each uses different vasoactive substances. However, each study, except for one study comparing Hispanics and Whites, and another comparing Japanese and German women, reveal some degree of racial variation in blood vessel reactivity. It has been demonstrated that the pH of Black skin is less than White skin; however, the studies that have demonstrated this have done so under different skin conditions and on different anatomic sites. Racial differences in lipid content are inconclusive. Additionally, there is insufficient and conflicting evidence to make conclusions regarding racial differences in skin biomechanics and skin microflora. Microscopic evaluation reveals that Black skin contains larger mast cell granules, and differences in stuctural properties and enzymes of mast cells compared with White skin, possibly accounting for differences in pruritus experienced by the individuals of these racial groups. There exists substantial evidence to support that Black skin has a higher TEWL, variable blood vessel reactivity, decreased skin surface pH, and larger mast cell granules compared with White skin. Although some deductions have been made about Asian and Hispanic skin, further evaluation needs to be done. Differences in WC, corneocyte desquamation, elastic recovery/extensibility, lipid content and skin microflora, although statistically significant, are inconclusive.

Ethnicity as a possible endogenous factor in irritant contact dermatitis: comparing the irritant response among Caucasians, blacks, and Asians

Irritant contact dermatitis (ICD) is a common dermatological diagnosis in which endogenous and exogenous factors have been implicated. This review explores ethnicity as a possible endogenous factor. While there is a clinical consensus that blacks are less reactive and Asians are more reactive than Caucasians, the data supporting this hypothesis rarely reaches statistical significance. The studies reviewed do not provide sufficient evidence to determine that race is a predisposing factor to the degree of irritation in ICD. We conclude that race could be a factor in ICD, which has practical consequences regarding topical product testing requirements, an ever-expanding global market, occupational risk assessment, and the clinical thinking about ICD. Pitfalls in defining differences are discussed.