EEMCO guidance for the assessment of stratum corneum hydration: electrical methods

BACKGROUND/AIMS

The improvement of stratum corneum hydration is one of the most important claims in the cosmetic industry.

METHODS

Objective assessment of moisturization can be done with devices based on electrical methods provided these instruments are used in an appropriate manner.

RESULTS

This paper deals with the biophysical basis behind these techniques and describes the most important variables, pitfalls and drawbacks related to measurements and current instrumentation. Individual-related and environment-related variables are also analyzed as well as study designs for predictive or use tests.

CONCLUSIONS

Practical suggestions for standardization of measurements are given.

Guidelines on sodium lauryl sulfate (SLS) exposure tests. A report from the Standardization Group of the European Society of Contact Dermatitis

This report reviews the clinical and histopathological reactions caused by sodium lauryl sulfate (SLS), and the non-invasive methods that can characterize these reactions. Furthermore, SLS exposure techniques and factors that may influence the outcome of these exposures are discussed. Finally, guidelines are introduced for each exposure technique in order to have a uniform approach to SLS testing in man. Since different study aims warrant different testing conditions, we have proposed 2 categories, namely susceptibility testing and provocative testing, tailored to the aim with which the study is performed.

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

The different reactivity of black and white skin after exposure to sodium lauryl sulphate (SLS) has been investigated. 9 white and 10 black male volunteers entered the study. The tests were performed on the back at 3 sites: untreated skin, skin pre-treated with occlusion and skin pre-delipidized. Irritant reactions were elicited applying 0.5% and 2.0% SLS via Finn chamber patch tests and monitored by means of laser Doppler velocimetry (LDV), transepidermal water loss (TEWL) and stratum corneum water content (WC). Higher TEWL, LDV, and WC values were recorded for 2.0% SLS when compared to 0.5% SLS and baselines. Pre-treatment with short-term occlusion generally increased values, while delipidization produced flattening of the data more detectable in whites than in blacks. Significant TEWL differences for the two concentrations were recorded in whites for the occluded site (P less than 0.02) while in blacks in the untreated (P less than 0.04) and delipidized (P less than 0.03) sites. LDV revealed significant changes in the untreated and pre-occluded white skin (P less than 0.05 and 0.01, respectively). In blacks, the values were significantly different only in the pre-occluded skin (P less than 0.01). Water content correlated with the visual score and was greatly increased in sites with strongly positive reactions (P less than 0.01). It appears that there are significant differences in the modulation of irritation, in the behavior of water barrier function and of the erythematous response between blacks and whites. Clinical correlations are discussed.

Microbiome in healthy skin, update for dermatologists

The skin is a complex barrier organ made of a symbiotic relationship between microbial communities and host tissue via complex signals provided by the innate and the adaptive immune systems. It is constantly exposed to various endogenous and exogenous factors which impact this balanced system potentially leading to inflammatory skin conditions comprising infections, allergies or autoimmune diseases. Unlike the gut and stool microbiome which has been studied and described for many years, investigations on the skin or scalp microbiome only started recently. Researchers in microbiology and dermatology started using modern methods such as pyrosequencing assays of bacterial 16S rRNA genes to identify and characterize the different microorganisms present on the skin, to evaluate the bacterial diversity and their relative abundance and to understand how microbial diversity may contribute to skin health and dermatological conditions. This article aims to provide an overview on the knowledge about the skin microbiota, the microbiome and their importance in dermatology.

Sensitive skin: an overview

Sensitive skin is a condition of subjective cutaneous hyper-reactivity to environmental factors. Subjects experiencing this condition report exaggerated reactions when their skin is in contact with cosmetics, soaps and sun screens, and they often report worsening after exposure to dry and cold climate. Although no sign of irritation is commonly detected, itching, burning, stinging and a tight sensation are constantly present. Generally substances that are not commonly considered irritants are involved in this abnormal response.Sensitive skin and subjective irritation are widespread but still far from being completely defined and understood. A correlation between sensitive skin and constitutional anomalies and/or other triggering factors such as occupational skin diseases or chronic exposure to irritants has been hypothesized. Recent findings suggest that higher sensitivity can be due to different mechanisms. Hyper-reactors may have a thinner stratum corneum with a reduced corneocyte area causing a higher transcutaneous penetration of water-soluble chemicals. Alterations in vanilloid receptors and changes in neuronal transmission have been described. Monitoring skin parameters such as barrier function, proclivity to irritation, corneocyte size and sensorial transmission can also be useful to identify regional differences in skin sensitivity.

In vivo biophysical characterization of skin physiological differences in races

The role of race in modulating skin responses has been investigated. Several parameters (skin thickness, transepidermal water loss, water content of the stratum corneum and skin biomechanics) have been measured using noninvasive tools in whites, Hispanics and blacks to assess whether the melanin content could induce changes in skin biophysical properties. Marked differences between races appear in stratum corneum water content and in skin extensibility, recovery and elastic modulus. Measurements done in different sun-exposed sites highlight the effects of solar irradiation on the skin and the role of melanin in preventing skin damage. The study shows that racial differences in skin physiology exist and are mainly related to the protective role of melanin present in races with darker skin. Moreover, differences in skin hydration are not fully explained according to the site and presence of hair.

The impact of airborne pollution on skin

Indoor and outdoor airborne pollutants modify our environment and represent a growing threat to human health worldwide. Airborne pollution effects on respiratory and cardiac health and diseases have been well established, but its impact on skin remains poorly described. Nonetheless, the skin is one of the main targets of pollutants, which reach the superficial and deeper skin layers by transcutaneous and systemic routes. In this review, we report the outcomes of basic and clinical research studies monitoring pollutant levels in human tissues including the skin and hair. We present a current understanding of the biochemical and biophysical effects of pollutants on skin metabolism, inflammatory processes and oxidative stress, with a focus on polyaromatic hydrocarbons and ground-level ozone that are widespread outdoor pollutants whose effects are mostly studied. We reviewed the literature to report the clinical effects of pollutants on skin health and skin ageing and their impact on some chronic inflammatory skin diseases. We also discuss the potential interactions of airborne pollutants with either ultraviolet radiation or human skin microbiota and their specific impact on skin health.

Glycerol accelerates recovery of barrier function in vivo

Two studies were performed to evaluate the influence of glycerol on the recovery of damaged stratum corneum barrier function. Measurements of transepidermal water loss and capacitance were conducted in a 3-day follow-up after tape stripping (study 1) and a 7-day follow-up after a barrier damage due to a repeated washing with sodium lauryl sulphate. In study 1 a faster barrier repair (transepidermal water loss) was monitored in glycerol-treated sites. Significant differences between glycerol open vs. untreated and glycerol occluded vs. untreated were observed at day 3. Stratum corneum hydration showed significantly higher values in the sites treated with glycerol+occlusion, compared with all other sites. In study 2 a faster barrier repair was seen in glycerol-treated sites, with significant differences against untreated and base-treated sites 7 days after the end of the treatment. Stratum corneum hydration showed highest values in the glycerol treated sites after 3 days of treatment. Glycerol creates a stimulus for barrier repair and improves the stratum corneum hydration; stratum corneum hydration is not strictly related to barrier homeostasis and can be optimized by different mechanisms and pathways. The observed effects were based on the modulation of barrier repair and were not biased by the humectant effect of glycerol. As the glycerol-induced recovery of barrier function and stratum corneum hydration were observed even 7 days after the end of treatment, glycerol can be regarded as a barrier stabilizing and moisturizing compound.

Testing for irritation with a multifactorial approach: comparison of eight non-invasive measuring techniques on five different irritation types

BACKGROUND

Non-invasive bioengineering methods are widely used in the assessment of irritant skin reactions.

OBJECTIVES

To assess the ability of eight non-invasive measurement techniques to distinguish changes in skin conditions over time, these changes being induced by five different irritants.

METHODS

The following techniques were compared in a multivariate analysis: laser-Doppler perfusion imaging (LDI), laser-Doppler flowmetry (LDF), transepidermal water loss (TEWL), visual scoring (VS), colorimetric measurements (Chromameter CR 200 a* and L* scales), Mexameter Hb scale (Mexa Hb) and capacitance (Corneometer CM 820). Irritants tested were sodium lauryl sulphate 2% (SLS), tape stripping (TS), tretinoin 0.05% (TRET), ultraviolet (UV) exposure to 30 W m(-2) UVB/95 W m(-2) UVA, and dithranol 0.5% (DIT). Measurements were performed at baseline and after 24, 48 and 72 h. The study was conducted on the upper back of 11 healthy volunteers of both sexes aged 27-51 years.

RESULTS

For DIT it was possible to discriminate over time with CR 200 a* and L*, VS, LDI, LDF and Mexa Hb. In SLS discrimination over time was seen with TEWL and LDF. Discrimination in TS was demonstrated for TEWL, VS, CR 200 a*, CM 820, LDF, LDI and Mexa Hb. In TRET discrimination ability was seen for LDI, LDF, Mexa Hb and VS. For UV it was possible to discriminate using VS, TEWL, LDF, LDI and Mexa Hb.

CONCLUSIONS

Different irritation patterns need different measurement modalities in order to give optimal discrimination over time.

Preliminary evaluation of in vivo reflectance confocal microscopy features of discoid lupus erythematosus

BACKGROUND

Discoid lupus erythematosus (DLE) can simulate other inflammatory diseases both clinically and histologically. In vivo reflectance confocal microscopy (RCM) is a noninvasive, reproducible imaging technique already reported to be useful in the evaluation of several inflammatory skin conditions such as contact dermatitis, psoriasis and Darier disease.

OBJECTIVES

The aims of our study were to define RCM features of DLE and to evaluate its feasibility in biopsy site selection.

METHODS

Discoid lesions were selected for RCM evaluation from 10 patients with an established diagnosis of DLE. Subsequently, a 4-mm punch biopsy of the same areas evaluated with RCM was rendered for histopathological examination.

RESULTS

A series of RCM features of DLE was identified and shown to correlate well with histopathological evaluation. Interface changes, as well as epidermal, dermal and adnexal inflammatory cell infiltration, were identified with RCM in a high percentage of the lesions. A limitation of RCM examination besides imaging depth was the inability to distinguish lymphocytes from other white blood cells.

CONCLUSIONS

The utility of RCM as a diagnostic tool for DLE awaits further evaluation, although it appears to be promising for biopsy site selection.

Sodium-lauryl-sulphate-induced cutaneous irritation. Comparison of white and Hispanic subjects

Reactivity of white and hispanic skin after exposure to sodium lauryl sulphate (SLS) has been investigated. The tests were performed on the back as follows: untreated skin, skin pre-treated with short-term occlusion and delipidized skin. Irritant reactions were induced by applying 0.5% and 2.0% SLS via Finn chamber patch tests and monitored by means of laser Doppler velocimetry (LDV), transepidermal water loss (TEWL) and stratum corneum water content (WC). Higher TEWL, LDV and WC were recorded for 2.0% SLS when compared to 0.5% SLS and baselines. Differences between white and hispanic skin reactivity were recorded. TEWL and WC responses showed a greater sensitivity in hispanics possibly reflecting a different modulation of the water barrier function after chemical exposure. On the other hand, the microcirculatory response, as long as detected with LDV, was similar in the 2 groups. Correlations between these data and findings observed in other races are discussed.

Differences in stratum corneum pH gradient when comparing white Caucasian and black African-American skin

This study assessed pH gradient changes in relation to stratum corneum (SC) depth and possible differences between white caucasian and black African-American skin. Ten white and eight black people entered the study. SC was progressively removed by cellophane tape stripping on the volar forearm and weighed with a microbalance. Transepidermal water loss (TEWL) and SC pH were measured every three tape strippings. Significantly increased TEWL and decreased pH values were found with increasing SC depth in both races. Significantly increased TEWL in black people was found after three and six tape strippings (P < 0.05 and 0.03, respectively); pH was significantly decreased in black people after three tape strippings (P < 0.005). No differences were found between the races after nine, 12 and 15 strippings, i.e. in the deeper SC layers. The data confirm that pH in the superficial SC layers decreases with SC depth; only total SC removal results in increased pH values. In the superficial layers, there are significant differences in both water evaporation and skin pH, possibly explaining the contradictory literature.

Cytokine profiles during infliximab monotherapy in psoriatic arthritis

BACKGROUND

Biological therapies are a new breakthrough in the treatment of psoriasis and psoriatic arthritis (PsA). Among these, tumour necrosis factor (TNF)-alpha antagonists such as infliximab and etanercept are the most promising as TNF is considered to be essential in driving cytokine cascade at sites of cutaneous and synovial inflammation in this disease.

OBJECTIVES

To evaluate the time-related response of serum cytokine release during infliximab monotherapy and assess serum cytokine levels in order to provide a fast, minimally invasive tool to monitor and/or predict efficacy of anti-TNF-alpha therapy.

METHODS

Twenty patients affected by PsA with Psoriasis Area and Severity Index (PASI) score between 0.4 and 42.8 were treated with infliximab for 30-42 weeks. The assessment of arthritis severity was performed using the American College of Rheumatology (ACR) criteria and ultrasonography evaluation. The treatment schedule consisted of infliximab (5 mg kg(-1) intravenously) at 0, 2 and 6 weeks and every 12 weeks on an individual basis determined by therapeutic results and adverse events reported. At baseline and before every infusion blood samples were taken to assess serum cytokine levels [TNF-alpha, interleukin (IL-6), E-selectin, vascular endothelial cell growth factor (VEGF), fibroblast growth factor (FGF), matrix metalloproteinase (MMP-2)].

RESULTS

Eighteen of 20 psoriatic patients achieved > 50% improvement and 14 of 20 patients attained > 75% improvement in the PASI score at 10 weeks. All arthritic patients achieved > 50% improvement (ACR-50) and 16 of 20 patients attained > 75% improvement (ACR-75) at 10 weeks. TNF-alpha did not decrease immediately during the first part of the study. A significant decrease was detected at week 12 (P < 0.01). In contrast, IL-6, VEGF, FGF and E-selectin showed significant decreases after early infliximab infusions. PASI was not correlated with TNF-alpha in the serum but was significantly correlated with FGF, VEGF and MMP-2. Treatment was well tolerated and there were no significant adverse events in most patients, other than an urticarial reaction and an autoimmune hepatitis.

CONCLUSIONS

Monotherapy with infliximab has to be considered an efficacious and safe treatment for PsA in comparison with traditional disease-modifying antirheumatic drugs. The resolution of cutaneous and synovial symptoms is not related to TNF-alpha serum levels in the initial phases. Apoptosis may play an important role in the modulation of the inflammatory response.

Impact of anatomical location on barrier recovery, surface pH and stratum corneum hydration after acute barrier disruption

BACKGROUND

It is not known whether distinct anatomical locations will respond with different recovery rates following acute barrier challenges.

OBJECTIVES

To investigate whether barrier parameters differ at five body sites during recovery from acute disruption.

METHODS

Acute barrier disruption was achieved by tape stripping and by acetone extraction of stratum corneum lipids. Transepidermal water loss (to assess barrier function), capacitance (for stratum corneum hydration) and skin surface pH were measured at each of five different body sites in 14 human volunteers. Individual measurements were obtained every 24 h for 96 h.

RESULTS

Lipid-rich skin areas (e.g. the forehead) were the most vulnerable to barrier disruption by either method. While acetone treatment affected barrier function and decreased stratum corneum hydration, tape stripping similarly altered barrier function but increased capacitance values. Although the effect of barrier disruption on surface pH appeared to vary with location, no significant pattern of variation emerged. Independent of the method used for barrier disruption, the pH normalized within 96 h.

CONCLUSIONS

Skin at different body sites shows distinct patterns of barrier recovery that are likely to be related to structural and physiological differences. Therefore, 'anatomically specific' regimens appear possible and relevant for the treatment of cutaneous disorders. In addition, adequate statistical analyses are essential to detect real differences in barrier recovery parameters.

Bioengineering and the patch test

Several non-invasive techniques based on different physical principles have been developed to investigate skin function and have been used for patch test assessment. In the present paper, the advantages and the defects of these methods are described in the light of the more recent data available in literature. Meanwhile, the eye and the fingers still remain the simplest method to assess skin irritancy. Bioengineering techniques could provide efficient recording systems for monitoring skin color, skin blood flow and barrier function damage, useful to the investigator rather than to the clinician.

The modulation of skin irritation

Irritant contact dermatitis (ICD) is a multifactorial disease, the onset and modulation of which depend on both endogenous and exogenous factors. Among the former, age, race, site, sex and history of dermatitis may all be important. Such variables can now readily be quantified by objective noninvasive techniques, such as measurement of transepidermal water loss (TEWL). Moreover, effects of irritants on the epidermis are related to the particular chemical properties of each molecule, contributing further to clinical heterogeneity. Release of cytokines and mediators may be initiated by a number of cells, including living keratinocytes and those of the stratum corneum, thus modulating inflammation and repair. Furthermore, differences in mechanisms of inflammation between acute and chronic ICD may exist, the former being characterized predominantly by inflammation, the latter by hyperproliferation and transient hyperkeratosis. These findings may explain the complexity and difficulty of investigating ICD. Better understanding and quantification of these mechanisms may lead to identification of high-risk individuals and more effective prevention and treatment.

Evaluation of efficacy of a skin lipid mixture in patients with irritant contact dermatitis, allergic contact dermatitis or atopic dermatitis: a multicenter study

Disturbances of skin barrier function occur in several skin diseases, e.g., atopic dermatitis (AD), irritant/allergic contact dermatitis (ICD, ACD). Skin barrier damage triggers the production of cytokines that stimulate lipogenesis which may also cause inflammatory processes. The aim of this study was to evaluate the efficacy of a topical skin lipid mixture in the treatment of ICD, ACD and AD. 580 consecutive patients suffering from ICD, ACD or AD were treated with a skin lipid mixture containing ceramide-3 and patented nanoparticles. Patients received the lipid mixture alone or in combination with topical corticosteroids until clearance or for 8 weeks. Both treatment groups statistically improved all parameters considered at week 4 and 8 as compared to baseline. Between the 2 treatment groups, there was a statistically significant difference in favour of combined therapy for (ICD, ACD, AD, respectively): erythema, pruritus and overall disease severity; erythema and pruritus; erythema, pruritus, fissuring and overall disease severity. No statistically significant difference was found for (ICD, ACD, AD, respectively): dryness, scaling and fissuring; scaling, fissuring and overall disease severity; dryness and scaling. Between the 2 ACD treatment groups, there was a statistically significant difference in favour of the skin lipid mixture for dryness. In conclusion, the study shows that balanced lipid mixtures are effective in improving barrier properties and the clinical condition of the skin in contact dermatitis.

Effects of water temperature on surfactant-induced skin irritation

Surfactant-induced irritant reactions may be elicited by several endogenous and exogenous factors. Among these, surfactant concentration, and duration and frequency of exposure play important rôles. The study focuses on the influence of water temperature in determining damage of the skin barrier. 10 subjects of both sexes entered the study. 4 areas (4 x 4 cm2) were randomly selected on the volar forearm and were treated with a daily open application of 5% sodium lauryl sulphate for 4 days. The solutions were at 3 temperatures: 4 degrees, 20 degrees and 40 degrees C. One site served as untreated control. On the 5th day, skin irritation was evaluated using transepidermal water loss (TEWL) measurements, erythema (a* value), skin reflectance (L* value), hydration (capacitance) and desquamation (stripping). The results show a significant effect of the solution's temperature in determining skin irritation (P < 0.001). Skin damage was higher in sites treated with warmer temperatures and a highly significant correlation (P < 0.001) between irritation and temperature was found. In conclusion, the study shows that water temperature during washing has an important effect on the onset of irritant contact dermatitis.

Cellulite: nature and aetiopathogenesis

Only a limited number of studies on cellulite have been published in the international literature and many of them reach somewhat antithetical conclusions. Consequently, it is not yet possible to reconcile the extreme differences of opinion which have lingered on for years concerning the nature of this disorder, as well as its origin and even the most basic aspects of its histopathological classification. It does not even have a recognized name: in fact, the term 'cellulitis' is used in scientific English to indicate a spreading gangrenous infection of the subcutaneous cellular tissue. The other terms used from time to time [panniculitis, lipodystrophy, edematofibrosclerotic panniculitis (EFP), liposclerosis, lipoedema, etc.] have quite different morphological and pathogenetic connotations in general. Over the last few decades, three major conflicting theories have emerged in relation to the ethiopathogenesis of cellulite. These indicate, respectively, the following causes: 1. Oedema caused by excessive hydrophilia of the intercellular matrix. 2. A homeostatic alteration on a regional microcirculatory level; this pathogenetic theory is summarized in a synthetic and self-explanatory denomination: EFP. 3. A peculiar anatomical conformation of the subcutaneous tissue of women, different from male morphology. These theories must all now be updated in the light of recent advances on the sophisticated and composite physiopathology of the adipose organ - which acts not only as a control device which regulates the systematic equilibrium of energy and modulates the food intake and the metabolism of other tissue substrate through a multiple glandular secretion of hormones and parahormones.

Racial differences in skin pathophysiology

Racial differences in skin function occur and may be responsible for differences in skin reactivity in physiologic and pathologic conditions. This article reviews the main racial anatomic and physiologic differences as well as mechanisms of irritation, sensitization, and drug absorption reported in the recent literature. Racial differences in transcutaneous penetration of chemicals and drug absorption have been described. Decreased transcutaneous penetration has been reported in black persons. In contrast, conflicting findings have been reported concerning some aspects of irritation and sensitization. Decreased erythematous reactions have been found in pigmented skin, whereas white persons have a stronger resistance to water barrier damage. Regional variation in skin function is more evident in fair skin because of the modifying effects of long-term UV exposure.

In vitro transepidermal water loss: differences between black and white human skin

In vivo transepidermal water loss studies are characterized by large inter-individual variability and biased by environmental effects and eccrine sweating. An in vitro technique for measuring transepidermal water loss (TEWL) was used to compare TEWL in two racial groups--blacks and whites. In both groups a significant correlation between skin temperature and increased TEWL was found (P less than 0.01). Furthermore, black skin had a significantly higher mean TEWL than white skin, corrected log TEWL 2.79 and 2.61 micrograms/cm2/h, respectively. The difference in TEWL between the groups could because measurements were made in the absence of eccrine sweating and other vital functions. The higher TEWL in black skin could be explained on the basis of a thermoregulatory mechanism. The anatomical and physiological differences in the stratum corneum between different races are discussed.