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.     

Tape-stripping method in man: comparison of evaporimetric methods

BACKGROUND/PURPOSE: If the occlusion time of a closed chamber evaporimeter on the skin is too long, saturation might occur. We previously compared an open chamber and a closed chamber device on healthy volunteers. Comparable data on stripped skin with higher evaporation rates are not available. This study compares the sensitivity and correlation of open and closed chamber devices in a tape-stripping human model. The amount of tape removed SC was also quantified with a protein assay method. METHODS: Ten healthy volunteers (six male and four female; seven Caucasians and three Asian; mean age 38+/-16) were enrolled. In a randomized manner, one forearm was measured by an open chamber device and the opposite by a closed chamber device. After recording baseline measurements, 20 strippings were taken on each test site with tape disks. Transepidermal water loss (TEWL) was measured at the end of 10 and 20 tape strippings at each test site. Stratum corneum (SC) aggregates in the strips was assayed. RESULTS: The mean values obtained from two devices were similar after 10 trips and 20 strips. There was no statistically significant difference. The closed chamber device showed a slightly higher (but not significant) inter-individual coefficient of variation. SC aggregates in the strips were similar and without a statistically significant difference. CONCLUSION: The study suggests that both devices might yield similar TEWL values on stripped human skin in vivo.     

Increased stratum corneum serine protease activity in acute eczematous atopic skin

Background Atopic dermatitis (AD) is a chronic inflammatory disease associated with changes in stratum corneum (SC) structure and function. The breakdown of epidermal barrier function in AD is associated with changes in corneocyte size and maturation, desquamation, lipid profiles, and some protease activities. Objectives The purpose of this study was: (i) to examine physiological changes in lesional (L) skin of acute eczematous AD, compared with nonlesional (NL) AD skin and healthy (H) skin, using sequential tewametry and SC protein analysis to estimate SC thickness; and (ii) to assess which serine proteases might be involved in pathogenesis. Methods Six subjects with H skin, six AD patients with NL skin and six AD patients with mild to moderate eczema (L skin) were enrolled. Skin was assessed using several noninvasive techniques but SC thickness was estimated using tewametry and SC protein content of D‐Squame strippings. SC integrity was determined by sequential tape stripping (D‐Squame) and infrared densitometry. Kallikreins, plasmin, urokinase and leucocyte elastase protease activities together with a novel SC tryptase‐like enzyme activity were quantified. Results Transepidermal water loss (TEWL) levels after D‐Squame stripping were elevated in L compared with NL and H skin at all sampling points (P < 0·05). Conversely, the amount of SC removed by sequential tape stripping was decreased in L skin, indicating increased intracorneocyte cohesion (P < 0·05). By correlating 1/TEWL values and SC removed as an estimate of SC thickness, a significantly thinner SC was observed in L compared with NL and H skin (P < 0·05). Elevated extractable serine protease activity was measured in AD skin in the order: SC tryptase‐like enzyme (45×), plasmin (30×), urokinase (7·1×), trypsin‐like kallikreins (5·8×) and chymotrypsin‐like kallikreins (3·9×). Leucocyte elastase activity was not detected in H and NL skin but was observed in AD SC samples (L skin). All enzymes were elevated in the deeper layers of L SC compared with NL and H SC samples. All consistently elevated SC protease activities were significantly correlated with the bioinstrumental data. Conclusions We report increased serine protease activities in acute eczematous AD, especially in deeper layers of the SC, including SC tryptase‐like enzyme, plasmin, urokinase and leucocyte elastase activities. These elevations in protease activities were associated with impaired barrier function, irritation, and reduced skin capacitance. Increased SC cohesion was apparent despite elevated TEWL during tape stripping, which would indicate reduced SC thickness in acute eczematous lesions of AD. Indeed, this was observed using an estimate of SC thickness.     

Skin sampling for Candida with adhesive tape

A simple and convenient method for the collection of Candida is described using skin strippings with vinyl plastic adhesive tape. On comparison with the use of a wet swabbing technique, the yeast was cultured from significantly more specimens collected by the stripping method. It was also shown that this method may be useful in quantification of the growth of Candida on culture per unit area of skin.     

Quantification of stratum corneum removal by adhesive tape stripping by total protein assay in 96-well microplates

BACKGROUND/AIMS: Examination of stratum corneum (SC) content with tape stripping and a colorimetric method is increasingly used. We examined the possible use of microplates in tandem with a colorimetric method to examine SC removed with tape stripping. As a corollary to this examination, the homogeneity of tape strips was examined. METHOD: The commonly used Lowry assay was adapted for 96-well plates. Tapes were divided into four regions and sample disks of 5 mm diameter were taken from each and analyzed for SC mass using the adapted Lowry assay. RESULTS: Homogeneity of SC removal over different areas across a tape strip is limited. CONCLUSION: Quantification of SC by means of a 96-well microplate-based colorimetric method is feasible and shortens the time of analysis. However, when using D-Squame tape disks, SC removal on a limited area of the tape is not predictive for SC removal on the entire tape as removal is inhomogenous. Therefore, SC protein extraction should be performed on a large enough area, eventually on the entire tape when quantifying SC mass removed by tape stripping.     

Functional assessment of a washing emulsion for sensitive skin: mild impairment of stratum corneum hydration, pH, barrier function, lipid content, integrity and cohesion in a controlled washing test

BACKGROUND/PURPOSE: Sensitive skin has been described as a skin type with higher reactivity than normal skin and exaggerated reactions to external irritants. Washing with soaps is harmful for barrier-related parameters. Cutaneous irritation induced by cleansing products under exaggerated test conditions, e.g. patch testing, is not necessarily predictive of the irritation occurring under standardized daily use conditions. The purpose of the study was to assess the effect of an improved washing solution for sensitive skin in a half-site comparison on barrier-related parameters. METHODS: Thirty healthy volunteers with self-reported sensitive and so-called problematic skin performed standardized washings with a soap-free washing emulsion with mild acidity (pH 5.5) for 3 weeks. Test areas were both forearms and the cheek. Non-invasive biophysical measurements of the following skin parameters, epidermal permeability barrier function measured as transepidermal water loss (TEWL), stratum corneum (SC) hydration, pH value, skin surface lipids, skin temperature and SC integrity/cohesion, were assessed prior to the first washing, on days 7, 14 and 21 after beginning the washing procedure. SC cohesion was quantified using two independent methods on D-Squame tapes: optical spectroscopy measuring the absorbance and a protein assay assessing the total protein (Bradford). Both methods showed a good correlation. SC integrity was quantified by measuring TEWL after sequential stripping with D-Squame tapes. RESULTS: The use of the washing emulsion led to a mild damage of the epidermal permeability barrier function with no marked difference to water application. Furthermore, a mild but significant dehydration was assessed after 21 days vs. baseline without any differences between the water-treated and the washing emulsion-treated forearm. On the cheek no dehydration was detectable but the lipid content was reduced under the washing emulsion. The pH value increased in all three test areas after 21 days, again without significant differences between water and the washing solution. SC cohesion was quantified using two independent methods on D-Squame tapes: optical spectroscopy measuring the absorbance and a protein assay assessing the total protein (Bradford). Both methods showed a good correlation. The SC cohesion decreased after 21 days on the water-treated as well as on the washing emulsion-treated arm. The decrease over time was significant when used the optical spectroscopy measuring. A standardized questionnaire revealed positive characteristics of the washing emulsion and good acceptance. CONCLUSION: The investigated standardized washing model with the endpoints epidermal barrier function, SC hydration, surface pH, skin surface lipids, skin temperature and SC integrity/cohesion showed only mild damage comparable to washing with water.     

Determination of stratum corneum lipid profile by tape stripping in combination with high-performance thin-layer chromatography

Abstract Intercellular lipids in the stratum corneum (SC) are responsible for the barrier function of mammalian skin. The main components of the SC lipids are ceramides, cholesterol, and free fatty acids, as established by thin-layer chromatographic analysis of lipids extracted from the human and mammalian SC. Up to now, for lipid analysis the extracts of the entire SC has been used and information on whether the lipid composition changes with the depth in the SC is scarce. Tape stripping is a technique which removes corneocyte layers step by step with an adhesive film. The use of this technique for lipid analysis was hampered by the contamination of lipid extracts with compounds co-extracted from the tape with organic solvents used for the extraction of SC lipids. The aim of the present study was to establish a suitable analytical method for the determination of the local SC lipid composition. For this purpose, the SC samples were collected by sequential stripping with Leukoplex tape in five healthy volunteers. The lipids were extracted with ethyl acetate:methanol mixture (20:80) and separated by means of HPTLC. The results of this study revealed that the free fatty acid level is highest and the cholesterol and ceramide levels lowest in the uppermost SC layers (about 4 strippings). The levels remained unchanged in the underlying SC layers. In these layers, the ceramide level was about 60 wt% and the free fatty acid and cholesterol levels were about 20 wt% each. Ceramides could be separated into seven different fractions and the relative amounts of individual ceramide fractions did not significantly change with the SC depth. Cholesterol sulfate levels were about 5% of total cholesterol and did not change with the SC depth, except for the for the first strip where the level was about 1%. The method developed makes it possible to study the differences in the SC lipid profile in healthy and diseased human skin with relation to the SC lipid organization and to the skin barrier function in vivo. Received: 2 August 2000 / Revised: 20 December 2000 / Accepted: 26 January 2001     

Cytokines at different stratum corneum levels in normal and sodium lauryl sulphate-irritated skin

BACKGROUND/PURPOSE: Cytokines play an important role in inflammatory and repair processes occurring in the skin. The objectives of this study were to determine the amounts of cytokines and protein isolated by tape stripping in the different layers of the stratum corneum (SC), and to compare normal skin with skin exposed in vivo to the irritant sodium lauryl sulphate (SLS). METHODS: In eight volunteers, we determined the amount of total and soluble protein and also interleukin-1alpha (IL-1alpha) in pooled tape strips obtained from the upper, intermediate and lower parts of the SC. Three different types of tape were compared (Diamond , D-squame or Sentega tape). In a separate study, 20 volunteers were repeatedly exposed to 0.1% SLS over a 3-week period. The amounts of IL-1alpha, IL-1RA and IL-8 in strips obtained from the three different SC levels of SLS-exposed skin were compared with an unexposed site. RESULTS: For normal skin, the amounts of soluble protein and IL-1alpha were similar for the three tapes. Diamond tape showed the highest yield of total protein. The total protein yield per strip decreased to lower SC levels, whereas soluble protein and IL-1alpha normalized by soluble protein did not change across the SC. After SLS induced skin irritation, IL-1alpha decreased and IL-1RA and IL-8 increased at increasing depth into the SC. CONCLUSIONS: Tape stripping is a suitable method to determine SC cytokine concentrations in human skin. With this technique, it is possible to study changes in cytokine concentrations at different SC layers after skin irritation.     

Millimeter wave reflectivity used for measurement of skin hydration with different moisturizers

Background/aims: A new non‐invasive method for determining the free water content in human skin has been developed. The method analyzes the reflection of millimeter (mm) wavelength electromagnetic waves. The amount of reflection of mm waves depends on an electrical property (namely, the permittivity) of the skin, and this depends upon the free water content of the various skin layers. The aim of the present study was to use the mm wave reflectometry method for determination of free water content in healthy skin treated with different hydrating substances. Methods: Skin lotion, pure water, glycerol, and petroleum jelly (an occlusive substance) were used for hydration of skin. The amount of free water was calculated using the permittivity values of skin layers found from fitting a three layer skin model to measured reflection data. The skin model consisted of (1) the stratum corneum (SC), (2) the viable epidermis plus the dermis, and (3) fat layers. Results: Mm wave reflection was significantly affected by the water content of the thick SC of the palm but not by the very thin SC of the forearm. Treatment of the forearm and palm skin with different hydrating substances produced notable changes of the free water content in the SC, but not in the viable epidermis or dermis. The greatest hydration was produced by pure water and skin lotion, and the lowest by petroleum jelly. However, petroleum jelly produced prolonged retention of water in the SC following its hydration by other moisturizers. The content of free water was found to return to its baseline value after removal of moisturizers in as short a time as 8.3 min. Conclusion: The study shows that mm wave reflectometry can be used as a sensitive technique for the non‐invasive determination of water content in living skin.     

Electrical determination of water content and concentration profile in a simulation model of in vivo stratum corneum

Because of its efficient water-holding capacity, healthy stratum corneum (SC) can stay soft and flexible under any environmental conditions. There may be, however, a great difference in water content within the SC between the lowermost layer that faces the wet underlying living tissue and the superficial portion of the SC that is exposed to the relatively dry ambient atmosphere. To better understand the water profile of the SC and also to verify the accuracy of measurements of high frequency conductance used to evaluate the hydration state of the skin surface, we devised a simple and convenient in vitro model of the SC that stimulates the in vivo setting of the SC. It consists of an isolated sheet of SC whose lower surface covers a pad of water-saturated filter paper, and its upper surface is exposed to the ambient atmosphere. By placing this model in environments with different relative humidities (RH), we confirmed that the recorded conductance values correlated well with the actual water content of the SC (r = 0.94). Using a model having five layers of SC sheets, the water content of the innermost portion of the SC was estimated to be equivalent to about 90% of its dry weight; this level of water content remaining relatively constant over a wide range of ambient RH except in extraordinarily humid environments above 90% RH when water began to accumulate excessively in the whole SC. Using this five SC-sheet model, it was clearly demonstrated that there was an almost straight water concentration gradient from the lowermost layer to the uppermost layer of the SC. We also confirmed that the skin conductance of the high frequency current correlated well with the water content of the superficial portion of the SC as well as with that of the whole SC, therefore, it is a good parameter of the hydration state of the superficial layer of the SC.     

我国正常人皮肤表面皮脂和水分含量的研究

目的：了解我国不同年龄、不同性别正常人皮肤角质层含水量、皮肤表面皮脂含量及皮肤皮脂的分泌速度。方法：利用皮肤表面皮脂测量仪和皮肤水分含量测量仪对我国北方325名正常人的前额及前臂屈侧皮肤皮脂量和皮肤含水量进行测量。结果：12岁以前,男女前额皮脂量无差异;13岁以后,男性前额的皮脂量明显高于女性。除36～50岁年龄组外,女性前额的皮脂分泌快于男性。男女前臂的皮脂量无差异。除男性13～35岁组的前额皮肤含水量高于女性外,其他各年龄组各部位男、女皮肤含水量无显著差别。13～35岁组男、女性前额的含水量均高于前臂。其他各年龄组前额和前臂皮肤含水量无明显部位差异。13-35岁组男性前额皮肤含水量最高。结论：正常人皮肤表面含水量和皮脂含量因性别、年龄和部位的不同而有差异。     

Acute barrier disruption by adhesive tapes is influenced by pressure, time and anatomical location: integrity and cohesion assessed by sequential tape stripping. A randomized, controlled study

BACKGROUND: Tape stripping is an established procedure in stratum corneum (SC) physiology research. Adhesive films are pressed to the surface of the skin and then removed. The superficial layers of the SC adhere to the film and are accessible for further investigations. Although this method is widely used, only scant information about standardization is known. Various protocols are used but are difficult to compare. OBJECTIVES: The aim of the present study was to investigate the effects of the type of tape, pressure, time, anatomical site and type of applied pressure. METHODS: Twelve healthy volunteers (age range 20-31 years) were entered in a randomized, controlled study with sequential tape stripping at the volar forearm, upper arm, cheek and back. Different methods (roller, stamp, thumb, stretched skin), total duration of applied pressure (2 s, 10 s), degrees of pressure (2 N stamp, 7 N stamp) and different tapes (D-Squame, Corneofix, Blenderm) were investigated and the impact on barrier function assessed by transepidermal water loss measurements. Furthermore, measurements of SC hydration, skin colour and skin surface pH were performed. Spectroscopic measurements and a Bradford protein assay to determine the mass of removed SC were carried out in parallel. RESULTS: The degree of barrier disruption, irritation and SC cohesion is influenced by the character of adhesive tapes, total duration of applied pressure (2 s, 10 s; 2 N, 7 N), the kind of method for pressure application (roller, stamp, thumb, stretched skin), anatomical site and condition before stripping (occlusion vs. nonocclusion). The spectroscopic assessment and Bradford protein assay determination showed a significant correlation (P < 0.0001; r = 0.7041). CONCLUSIONS: The present study showed significant differences between different factors on controlled barrier disruption. The results indicate the importance of defining these factors when a study is initiated and when results of different studies should be compared. Based on our data we propose using a 2 N stamp for a duration of 2 s on 15 sequential D-Squame tape strips on the volar forearm and then discarding the first and second strips. This approach allows the performance of a standardized study with a reasonable amount of resources.     

Gender-related differences in the physiology of the stratum corneum

BACKGROUND: Only few studies on gender-related differences in skin physiology have been performed--and they provided conflicting results. OBJECTIVE: In the present study, the effect of gender on the physiology of the stratum corneum was studied. METHODS: The physiological parameters transepidermal water loss, pH value, hydration and sebum content were determined on the flexor forearms of 6 female and 6 male volunteers. In addition, stratum corneum samples, removed by tape stripping, were studied for amount, spectroscopic properties, protein content, and mass. RESULTS: The skin of women was characterized by a significantly higher pH value (5.6 +/- 0.4) than that of men (4.3 +/- 0.4, p < 0.05). Protein absorption was the only other parameter significantly dependent on gender (p < 0.05). Both effects might be caused by differences in human biology, such as hormonal status. CONCLUSION: Therefore, the gender of the volunteers should be considered in dermatologic studies.     

Depth profiling of Stratum corneum hydration in vivo: a comparison between conductance and confocal Raman spectroscopic measurements

Abstract:  The high-frequency electrical conductance of tape-stripped human skin in vivo can be used to evaluate the hydration profile of Stratum corneum (SC). Tape-stripping provides access to the underlying SC layers, and the conductance of these layers (as measured by the Skicon instrument) correlates well with their water content, as demonstrated by independent confocal Raman spectroscopic measurements. The correlation shows high inter-individual variance and is not linear over the full measurement range of the instrument, but is helpful to discriminate between dry, normal and highly hydrated SC. The depth profile of hydration in tape-stripped SC corresponds to the one in intact SC only if the barrier function of the skin is not impaired. Thus, conductometry of tape-stripped skin must be used in conjunction with a method that allows to estimate the barrier damage inflicted to SC during the tape-stripping procedure, for example, measurement of the trans-epidermal water loss. The methodology described here is simple, rapid and minimally invasive, and it employs commercially available instrumentation that is cheap, portable and easy to use. This approach is applicable to in vivo estimation of the SC hydration in studies in the areas of dermatology, skin care and transdermal drug delivery.     

Depth profiling of stratum corneum biophysical and molecular properties

Background The barrier function of the skin may be characterized by a number of biophysical and molecular methods. Variation in the barrier properties as a function of depth has not been explored in detail. Objectives To characterize changes in corneocyte surface area, corneocyte maturity, selected protease activities and transepidermal water loss (TEWL) in the ventral forearm with increasing depth. Methods The left mid‐ventral forearm of 22 healthy volunteers was selected as the study site. After tape stripping, corneocyte maturity and surface area were assessed. The protease activity of the desquamatory kallikrein proteases, KLK5 and KLK7, and inflammatory tryptase was measured using a fluorogenic probe assay. Protein content and TEWL were also recorded. Results Corneocyte maturity and surface area decreased with increasing number of tape strippings, i.e. depth into the skin. More mature corneocytes were typically larger than less mature corneocytes. The protease activities of both the desquamatory and inflammatory enzymes together with the protein content were highest in the outer layers of the stratum corneum and decreased with depth. As expected, TEWL increased as more stratum corneum layers were removed. There were no statistical differences between men and women or caucasian and black subjects for all of the parameters studied. Conclusions The techniques used in this study provide rapid noninvasive measures of the spatial distribution of corneocyte maturity and surface area as well as protease activity and protein content within different levels of the stratum corneum layers. The methods used will allow mechanistic insight into the effects of formulation excipients and active ingredients on epidermal turnover and skin barrier function.     

Stratum corneum adhesive tape stripping: influence of anatomical site, application pressure, duration and removal

BACKGROUND: Tape stripping is a common method for investigating stratum corneum (SC) physiology as well as bioavailability and bioequivalence of topical drugs. OBJECTIVES: To investigate the influence of procedures (anatomical site, pressure, pressure duration, tape removal rate) inherent in each stripping protocol on changes in skin physiology. METHODS: Tape stripping was performed using tapes on the forearm, forehead and back. On the forearm different pressures (165 and 330 g cm(-2)), durations of pressure (2 and 10 s), and removal rate (slow and rapid removal) were used. Changes in skin physiology were evaluated by measurement of transepidermal water loss (TEWL) and hydration. RESULTS: A significant influence of all parameters on the TEWL increase as a function of tape strip number was observed. The fastest increase was demonstrated on the forehead, followed by the back and, lastly, the forearm. Rapid removal produced a protracted increase in comparison with slow removal. Pressure for 10 s induced a faster increase in TEWL than 2 s pressure. Likewise, pressure at 330 g cm(-2) induced an earlier increase than pressure at 165 g cm(-2). Skin hydration was not influenced by the variables tested. CONCLUSIONS: Tape stripping results are influenced dramatically by all investigated parameters. A dynamic SC stress test to investigate SC cohesion more closely is proposed based on the present observations.     

Skin capacitance imaging and corneosurfametry. A comparative assessment of the impact of surfactants on stratum corneum

Silicon image sensor (SIS) technology was recently introduced as an innovative tool (SkinChip, L'Oréal) providing sensitive imaging of the skin capacitance. This method can detect discrete focal variations in skin surface hydration, and thus early discrete manifestations of skin irritation induced by surfactants. In the present in vivo study, 2 neat and diluted shampoos, and 5% and 10% sodium laurylsulfate solutions were tested on human skin. Each surfactant solution was gently rubbed on the skin using wet hair wicks mimicking the casual use of a shampoo on the scalp. Clinical and SIS evaluations were carried out. In addition, the same products were tested using the ex vivo corneosurfametry bioassay performed on human stratum corneum (SC) harvested by cyanoacrylate skin surface strippings. The colourimetric index of mildness (CIM) was measured on these samples. The product reactivity with the SC was recognized by darker skin capacitance images, and by both lowered SkinChip-generated values and lowered CIM values. The extent in changes varied according to the nature of the test products and their concentrations. The SkinChip image changes likely corresponded to the acute surfactant-induced water swelling of the corneocytes. Skin capacitance imaging and corneosurfametry allow to disclose discrete surfactant-induced alterations of corneocytes.     

2D luminescence imaging of physiological wound oxygenation

In cutaneous wound healing, the role of oxygen in vivo is poorly understood. We studied wound surface pO(2) during physiological wound healing in humans. Split-thickness skin graft donor sites (n=12) served as standardized wound models. Wound surface pO(2) was measured at 1, 6 and 14days after split-skin harvesting using two-dimensional luminescence lifetime imaging (2D-LLI) of palladium(II)-meso-tetraphenyl-tetrabenzoporphyrin (Pd-TPTBP) in polystyrene-co-acrylonitrile (PSAN) particles on transparent foils. In another experiment, we removed the stratum corneum (SC) on the volar forearm (n=10) by tape strippings to study the impact of the SC on the epidermal oxygen barrier. Split-skin donor site pO(2) significantly decreased during the time course of physiological healing. Regional differences in pO(2) within donor site wounds were visualized for the first time in literature. No difference was found in pO(2) before and after SC removal, showing that the SC is not a major constituent of the epidermal oxygen barrier.     

Hand and forearm skin: comparison of their respective responsiveness to surfactants*

Background/aims: Skin compatibility of detergent products is usually evaluated using predictive tests where products are applied on the back or the forearm of the volunteers, even if those products come more readily into contact with consumers’ hands. The current study aimed at comparing the skin responsiveness of hands and volar and dorsal forearms to a surfactant solution. Method: Volunteers soaked simultaneously their forearms and hands in a solution of anionic surfactants, at 40 °C for 20 min, thrice a day and for 2 consecutive days. Skin condition on the hands, and the volar and dorsal forearms was evaluated by clinical examination and instrumental measurements. Results: Significant differences were observed at baseline for various skin parameters, especially those related to skin dryness. After repetitive contacts with the surfactant solution, a parallel evolution of most skin parameters was observed – i.e., an absence of change in instrumentally measured erythema and transepidermal water loss, a similar decrease in corneometry values, and a similar increase in staining of the stratum corneum strippings and in clinical dryness. However, an opposite effect of the soakings on the cohesiveness between corneocytes harvested by tape strippings from hand and forearm was observed. Conclusion: For most parameters, skin responsiveness to surfactants appears to be quite similar on the hands and forearms. It is inferred that forearms can be conveniently used to predict interaction of surfactants with hands.     

Appearance benefits of skin moisturization

Background/purpose: Skin hydration is essential for skin health. Moisturized skin is generally regarded as healthy and healthy looking. It is thus speculated that there may be appearance benefits of skin moisturization. This means that there are corresponding changes in the optical properties when skin is moisturized. Methods: The appearance of the skin is the result of light reflection, scattering and absorption at various skin layers of the stratum corneum, epidermis, dermis and beyond. The appearance benefits of skin moisturization are likely primarily due to the changes in the optical properties of the stratum corneum. We hypothesize that the major optical effect of skin moisturization is the decrease of light scattering at the skin surface, i.e., the stratum corneum. This decrease of surface scattering corresponds to an increase of light penetration into the deeper layers of the skin. An experiment was conducted to measure the corresponding change in skin spectral reflectance, the skin scattering coefficient and skin translucency with a change in skin hydration. In the experiment, skin hydration was decreased with the topical application of acetone and alcohol and increased with the topical application of known moisturizers and occlusives such as PJ. Result and conclusion: It was found that both the skin spectral reflectance and the skin scattering coefficient increased when the skin was dehydrated and decreased when the skin was hydrated. Skin translucency increased as the skin became moisturized. The results agree with the hypothesis that there is less light scattering at the skin surface and more light penetration into the deeper skin layers when the skin is moisturized. As a result, the skin appears darker, more pinkish and more translucent.