Ceramide 1 and ceramide 3 act synergistically on skin hydration and the transepidermal water loss of sodium lauryl sulfate-irritated skin

Background  Stratum corneum intercellular lipids, such as ceramides, play an important role in the regulation of skin water barrier homeostasis and water-holding capacity.
Aim  To evaluate the potential water retention capacity of control emulsion and three oil-in-water (o/w) emulsions containing ceramide 1, ceramide 3, or both.
Methods  Fifteen healthy Asian women (age, 20–30 years) with healthy skin, pretreated with sodium lauryl sulfate (SLS), applied the tested emulsions twice daily over a period of 28 days. Skin hydration and transepidermal water loss (TEWL) values were measured on the indicated days with a Corneometer®825 and a TEWAMETER TM210, respectively.
Results  The maximum increase in skin humidity was reached after 4 weeks, with values of 21.9 ± 1.8% and 8.9 ± 0.9% for emulsion C and control emulsion, respectively. The maximum decrease in TEWL was also reached after 4 weeks, with values of 36.7 ± 4.7% and 5.1 ± 0.8% for the same emulsions.
Conclusions  It can be concluded that all the tested ceramide-containing emulsions improved skin barrier function when compared with untreated skin. There was some indication that ceramides 1 and 3 contained in emulsion C might exert a beneficial synergistic effect on skin biochemical properties, such as skin hydration and TEWL, and play a key role in the protection mechanism against SLS irritation.     

Repair of acetone- and sodium lauryl sulphate-damaged human skin barrier function using topically applied emulsions containing barrier lipids

BACKGROUND: It is generally acknowledged that well-formulated moisturizing skin care products can restore disturbed barrier function that can be assessed by transepidermal water loss (TEWL) measurements. When ceramides and/or other barrier lipids are incorporated, it is, however, not always clearly demonstrated which ingredients of the formulation exert the beneficial effects. OBJECTIVES: In this study the effects of topically applied ceramide-containing mixtures on the barrier repair of sodium lauryl sulphate (SLS)- and acetone-induced skin damage have been studied in human volunteers. TEWL and stratum corneum hydration measurements were carried out. The emulsions applied contained either a mixture of two types of ceramides, CerIII and CerIIIB (emulsion 1) or a complete mixture of ceramides III, IIIB and VI together with phytosphingosine, cholesterol and the free fatty acid linoleic acid (emulsion 2). RESULTS: After SLS damage, it was observed that barrier recovery was significantly accelerated by topical application (14 days, 2 x/d) of emulsion 2 compared with the results obtained with emulsion 1. Corneometrical results were not relevant due to the occurrence of scaly fissured skin, failing to provide a good skin/probe contact. Although no effect on TEWL could be observed, the improvement of skin hydration after acetone treatment and a single application of the emulsions, was significantly more positive for emulsion 2 than for emulsion 1. CONCLUSIONS: The investigative methods used in this study show that ceramides combined with other skin lipids can improve barrier repair after damage.     

EIectrical impedance and transepidermal water loss of healthy human skin under different conditions

Background/aims: The skin barrier function is a multidimensional quality, which can be defined by a combination of noninvasive measurements, including EIectrical impedance (EI) and transepidermal water loss (TEWL). Methods: TEWL and EI were determined on in five different areas of the body in 25 healthy volunteers. The effects of hydration (a 15 min water bath, a 1 h occlusion and application of an oil-in-water emulsion combined with occlusion) were measured on the volar forearm. Results: EI was highest in the axillary region, followed by the cheek, spinal region, presternal area and upper arm. TEWL was highest in the axillary region, followed by the cheek. Lowest levels were detected in the spinal region, the presternal region and the upper arm. The water bath increased EI but not TEWL. After 1 h occlusion TEWL was not increased and EI decreased, which corresponds to stratum corneum hydration. After a single application of an oil-in-water emulsion, we observed a reduction of EI and an increase of TEWL. The simultaneous use of occlusion and application of an emulsion led to the most significant reduction of EI. TEWL was increased during the following 30 min. Conclusions: EI and TEWL show a topological variability. Acute hydration increased EI but occlusion and/or moisturizing decreased EI. Acute hydration and occlusion alone did not significantly affect TEWL, but moisturizing in combination caused a longer lasting TEWL increase. To examine the stratum corneum function, the use of different noninvasive techniques seem to provide more complex information.     

Electrical measurement of moisturizing effect on skin hydration and barrier function in psoriasis patients

Transepidermal water loss (TEWL) in psoriatic skin lesions seems to be related to the severity of the psoriasis, and the electrical capacitance and conductance of the skin are indicators of the hydration level of the stratum corneum. We compared the characteristics of these electrical measurements, in assessing the persistent effect of a moisturizing cream on skin hydration and barrier function in psoriasis patients. Seventeen Korean psoriasis patients were recruited. Their right leg was treated with the moisturizer twice daily for 6 weeks, while their left leg was used as the control site. For each patient, one psoriatic plaque on each leg was selected as the involved psoriatic lesion. Uninvolved psoriatic skin was regarded as the apparently healthy looking skin 4-5 cm away from the periphery of the psoriatic lesion. The TEWL, electrical capacitance and conductance were measured, in order to evaluate the barrier function and hydration level of the stratum corneum. The clinical and biophysical data for each patient were recorded at the start of the study and after 2, 4 and 6 weeks. The degree of skin dryness at the applied area improved progressively. The electrical capacitance at the treated psoriatic lesion increased significantly after 2 weeks, and this improvement was maintained during the entire study period. However, no noticeable change was observed in the electrical conductance. The TEWL showed an inverse pattern to that of the skin capacitance, decreasing during the study period. The skin capacitance and TEWL exhibited good correlation with the visual assessment of skin dryness, but the skin conductance did not. Our data suggest that electrical capacitance and TEWL may be useful in the evaluation of the effect of a moisturizer on the hydration status and barrier function of psoriatic skin.     

Improvement of mild inflammatory changes of the facial skin induced by winter environment with daily applications of a moisturizing cream. A half-side test of biophysical skin parameters, cytokine expression pattern and the formation of cornified envelope

OBJECTIVE: Based on our previous findings that, reflecting mild inflammation, the exposed facial skin shows much poorer functional properties of the stratum corneum (SC) in the dry and cold winter than those evaluated in the same individuals in the warm and humid summer time, we conducted a half-side test on the face to determine how the facial skin changes induced by a winter environment are improved by daily applications of a moisturizing cream as assessed by non-invasive biophysical and cytological methods. METHODS: One side of the face of 16 young females was treated with a moisturizing cream twice daily for 6 weeks, with the other side serving as the non-treated control. Before treatment, 3 and 6 weeks after the start of the treatment, high-frequency conductance as a parameter of the skin surface hydration, transepidermal water loss (TEWL), a parameter of the water barrier function of the skin, and the skin surface lipid level were measured on the cheeks. Obtaining the SC from the skin surface by adhesive tape, interleukin (IL) 1alpha and IL-1 receptor antagonist (IL-1ra) in the SC and cornified envelope (CE) maturation were determined. RESULTS: At first, baseline measurements conducted before treatment showed rather high TEWL values suggestive of an impaired skin barrier. During the treatment with the moisturizing cream, significantly higher conductance values and lower TEWL values were found on the moisturizer-treated side, accompanied by a decreasing IL-1ra/IL-1alpha ratio and immature CEs. CONCLUSION: These results suggested that the daily application of a moisturizing cream is effective in improving mild subclinical inflammation that is induced on the facial skin by the winter environment.     

Silk sericin as a moisturizer: an in vivo study

Background Excessive transepidermal water loss (TEWL) is the one of the causes of dry skin, and skin moisturizers have been used to overcome it. Aim The purpose of this research was to study the moisturizing effect of sericin, a silk protein. Because silk sericin has resemblance with the natural moisturizing factor (NMF), it has been studied for its application in skin cosmetics. Methods Sericin gels were prepared using sericin solution and with pluronic and carbopol as stabilizers. The gels were applied on the skin of healthy human volunteers and its moisturizing efficiency was evaluated by measuring the skin hydroxyproline content, impedance, TEWL, and scanning electron microscopy (SEM) results. Results Decrease in skin impedance, increase in hydroxyproline level, and hydration of epidermal cells revealed the moisturizing effect of sericin, whereas decrease in the value of TEWL may be attributed to occlusive effect, which prevents water loss from the upper layer of the skin. Skin surface topography revealed the smoothness of the upper layer of the skin as a result of moisturization. Conclusion Increase in the intrinsic moisturization of skin by sericin may be attributed to restoration of the amino acids and its occlusive effect. Thus, it would become a promising and important moisturizing ingredient in moisturizing formulations.     

Effects of glycerol on human skin damaged by acute sodium lauryl sulphate treatment

Glycerol, widely used as humectant, is known to protect against irritants and to accelerate recovery of irritated skin. However, most studies were done with topical formulations (i.e. emulsions) containing glycerol in relatively high amounts, preventing drawing conclusions from direct effects. In this study, acute chemical irritations were performed on the forearm with application of a 10% sodium lauryl sulphate (SLS) aqueous solution under occlusion for 3 h. Then, glycerol aqueous solutions from 1 to 10% were applied under occlusion for 3 h. After elimination of moist excess consecutive to occlusive condition, in ambient air for 15 and 30 min, skin barrier function was investigated by dual measurement of skin hydration and transepidermal water loss (TEWL). Treatments with SLS solution under occlusion significantly increased TEWL and decreased skin hydration as assessed by capacitance measurements. The SLS irritant property was raised by the occlusion and the water barrier function as well as water content appeared impaired. Recovery with glycerol at low doses was remarkable through a mechanism that implies its hygroscopic properties and which is saturable. This precocious effect acts through skin rehydration by enhancing water-holding capacity of stratum corneum that would facilitate the late physiological repair of impaired skin barrier. Thus, glycerol appears to substitute for natural moisturizing factors that have been washed out by the detergent action of SLS, enhancing skin hydration but without restoring skin barrier function as depicted by TEWL values that remained high. Thus, irritant contact dermatitis treated with glycerol application compensate for skin dehydration, favouring physiological process to restore water barrier function of the impaired skin. Empirical use of glycerol added topical formulations onto detergent altered skin was substantiated in the present physicochemical approach.     

Defective barrier function accompanied by structural changes of psoriatic stratum corneum

Although barrier function of psoriatic skin is shown to be decreased by measuring transepidermal water loss (TEWL), few reports exist examining other physical skin properties and components including stratum corneum hydration, natural moisturizing factor (NMF), free fatty acids (FFA), β‐sheet and α‐helix ratio of structural protein(s), and sebum content. We compared the skin properties and components of normal, involved and uninvolved skin of psoriasis. Using a corneometer and attenuated total reflection‐infrared spectrometer, we measured TEWL, stratum corneum hydration, NMF, FFA, β/α ratio and sebum in psoriasis vulgaris patients and healthy controls. TEWL and β/α ratio of involved psoriatic skin were significantly increased compared with uninvolved skin and normal control skin. In contrast, stratum corneum hydration , NMF and FFA, but not sebum, are significantly decreased in the involved skin compared with uninvolved skin and normal skin. TEWL and stratum corneum hydration returned to the normal levels following clinical improvement of the lesion. Barrier function and hydration of psoriatic skin are defective and secondary structure in stratum corneum protein is altered in the involved psoriatic skin.     

The 24‐hr, 28‐day,and 7‐day post‐moisturizing efficacy of ceramides 1, 3, 6‐II containing moisturizing cream compared with hydrophilic cream on skin dryness and barrier disruption in senile xerosis treatment

Direct replacement of decreased ceramides in the stratum corneum can be efficacious for skin hydration, skin barrier function, and skin pH. Our study aimed to evaluate the 24‐hr, 28‐day, and 7‐day post‐moisturizing efficacy of ceramide‐containing moisturizer in senile xerosis treatment. A split site, double‐blinded, randomized, controlled study was conducted in 24 senile subjects (91.7% females, mean age 54.83 ± 5.45 years) with mild to moderate xerosis, who were randomized to receive ceramide‐containing moisturizer or hydrophilic cream, daily applied on each side of the shin. A single application of ceramide‐containing moisturizer increased skin hydration, while improving transepidermal water loss (TEWL) and skin pH for up to 24 hr, with statistically significant difference. After 28 days of twice‐daily application, more significant improvement on skin hydration, barrier function, and skin pH was observed in those with ceramide‐containing moisturizer at all‐time points. At day 28, there was a statistically significant decrease of hemoglobin index, wrinkle, and texture on the ceramide treated side. The 7‐day post‐moisturizing efficacy on the ceramide treated side was superior for skin hydration, TEWL, skin pH, and wrinkle. Thus, the ceramide‐containing moisturizer can be a novel promising treatment for senile xerosis.     

Incorporation of ceramide 3B in dermatocosmetic emulsions: effect on the transepidermal water loss of sodium lauryl sulphate-damaged skin

BACKGROUND: In previous work we reported on the efficacy of cosmetic body lotions enriched with skin-identical lipids to reduce the transepidermal water loss (TEWL) of ageing and sodium lauryl sulphate (SLS)-damaged skin. The observations made depended on the experimental design and clearly raised the question of the importance of the galenic formulation of skin ceramide-containing products. OBJECTIVES: The aim of the present work was to study the different galenic forms in which ceramide 3B (0.2% w/v) can be incorporated into common o/w emulsions. In addition, we investigated whether supplementation of skin care products with ceramide 3B enriched with penetration enhancers and coemulsifiers could exert a beneficial effect on barrier function, done by measuring their effects on the TEWL of SLS-induced scaly skin. RESULTS: We found that the technique of incorporating ceramide 3B into the o/w emulsions was important for their final stability. However, no additional positive effect on the TEWL values of SLS-damaged skin could be observed when the efficacy of the ceramide-containing emulsions was compared with that of proper controls. CONCLUSIONS: Although suitable galenic formulas were developed, no positive effect on TEWL could be observed when ceramide 3B was added in a final concentration of 0.2% (w/v) to different o/w emulsions and applied to SLS-damaged skin.     

Transepidermal water loss and skin capacitance alterations among workers in an ultra-low humidity environment

No studies have been performed evaluating skin barrier alterations in humans exposed to ultra-low humidity (ULH) in spite of several lines of evidence from animal experiments suggesting that the skin barrier is altered on exposure to ULH. The objectives of this study were to assess barrier function changes in workers occupationally exposed to ULH (relative humidity 1.5%), and to evaluate whether the exposure duration shows a dose-response relationship with transepidermal water loss (TEWL) and skin capacitance. A total of 49 male workers exposed to ULH for 12 h per working day were classified into five subgroups based on their ULH exposure duration (<0.5 months, 0.5–1.0 month, 1.1–10.0 months, 10.1–20.0 months, and >20.0 months). A group of 12 age-matched male laboratory workers from a normal humidity environment were recruited as a control group. TEWL and skin capacitance were measured to evaluate their skin barrier function. TEWL measurements showed a significant decline (8.3±0.4 vs 10.0±0.4 g m^–2 h^–1, P<0.05) but no differences were found in skin capacitance (39.7±1.3 a.u. vs 45.0±2.4 a.u., P=0.68) between the whole ULH exposure group and the control group. Maximum decreases in TEWL and skin capacitance were seen in the subgroups exposed for <0.5 months and 0.5–1.0 month, respectively. Almost completely natural recovery occurred in skin capacitance after 20 months ULH exposure, in contrast to less than 90% recovery in TEWL. Three stages were defined according to the pattern of alterations in TEWL and skin capacitance in relation to ULH exposure duration. A positive association between TEWL and skin capacitance occurred in the control group and stage I but a negative correlation in stage II. No correlation was found in stage III. Our study demonstrated that workers exposed to a ULH environment could exhibit skin barrier alterations. Both TEWL and skin capacitance decreased within 2 weeks of ULH exposure. The maximum alterations in TEWL and skin capacitance occurred during 0.5–1.0 months and 2 weeks, respectively. TEWL recovered partially and more slowly than skin capacitance which recovered earlier and almost completely.     

Percutaneous penetration of sodium lauryl sulphate is increased in uninvolved skin of patients with atopic dermatitis compared with control subjects

BACKGROUND: Involved regions of the skin in patients with atopic dermatitis (AD) have been shown to have higher transepidermal water loss (TEWL), indicating a compromised skin barrier. Whether uninvolved skin also has diminished barrier characteristics is controversial. OBJECTIVES: To study the penetration of sodium lauryl sulphate (SLS) into uninvolved skin of patients with AD compared with the skin of control subjects. METHODS: Percutaneous penetration was assessed using the tape stripping technique on the stratum corneum (SC). Twenty patients with AD and 20 healthy subjects were exposed to 1% SLS for 4 h on the mid-volar forearm. After the end of exposure the SC was removed by adhesive tape. The amount of SLS was determined in each consecutive strip. Fick's second law of diffusion was used to deduce the diffusivity and the partition coefficient of SLS between water and the SC. RESULTS: The SC thickness was similar in both groups; however, the TEWL was higher in patients with AD compared with that of the control group (mean+/-SD 8.4+/-4.3 and 6.3+/-2.0 g m-2 h-1, respectively). There was a correlation between SC thickness and TEWL in control subjects but no correlation was found in patients with AD. The diffusivity of SLS through uninvolved AD skin was higher compared with normal skin (mean+/-SD 12.7+/-5.8x10(-9) and 6.2+/-3.0x10(-9) cm-2 h-1, respectively), while the partition coefficient between SC and water was lower (mean+/-SD 137+/-64 and 196+/-107, respectively). CONCLUSIONS: The results show a different penetration profile of SLS into the SC of patients with AD compared with control subjects. This indicates that even noninvolved skin in patients with AD has altered barrier characteristics, emphasizing the importance of skin protection and prevention of skin contact with chemicals.     

Increased stratum corneum turnover induced by subclinical irritant dermatitis

The chronic effects of the irritant sodium lauryl sulphate (SLS) on stratum corneum (SC) barrier function, determined by transepidermal water loss (TEWL) measurements and on epidermal cell kinetics, estimated by stratum corneum turnover time (SCTT) determination (dansyl chloride staining method), were investigated in 18 healthy female volunteers. SLS (7.5%) was applied without occlusion for 20 min once daily, over a period of 3 weeks (5 days a week) on dansyl chloride-stained skin and on untreated skin. SCTT of untreated skin (19.3 +/- 0.8 days; mean +/- SEM) was not changed by daily treatment with water (control) (19.3 +/- 2.0) but was significantly reduced by SLS (10.9 +/- 0.6; P less than or equal to 0.0001; compared to controls). However, TEWL was increased in SLS-treated sites 1.5-fold after 4 days of treatment (5.3 +/- 0.6 vs. 3.5 +/- 0.3; P less than 0.001). At the end of the second week, TEWL was increased 2.6-fold and after 3 weeks TEWL was 3.3 times higher than in controls 13.0 +/- 1.6 vs. 3.9, P less than or equal to 0.0001). The intensity of SLS-induced irritation as measured by TEWL was significantly correlated with baseline TEWL (r = 0.50; P less than or equal to 0.02) and significantly negatively correlated with SCTT of SLS treated sites (r = -50; P less than or equal to 0.02) but not with SCTT of untreated skin (r = 0.19).     

Functional assessment of the stratum corneum under the influence of oral aromatic retinoid (etretinate) in guinea-pigs and humans. Comparison with topical retinoic acid treatment

Clinically we have noted that the skin of patients treated with long-term oral etretinate becomes uniformly soft and smooth to touch, like facial skin that becomes smoother and less wrinkled following treatment with topical tretinoin. This suggests that retinoids, whether used systemically or topically, alter the physical properties of the skin, particularly of the stratum corneum (SC). To study the influence of retinoids on the SC, we serially assessed the functional properties of the SC non-invasively in retinoid-treated humans and experimental animals. SC hydration and barrier function were assessed by measurement of high-frequency conductance and transepidermal water loss (TEWL), respectively. Daily application of topical retinoic acid creams was found to rapidly induce a time- and dose-dependent, linear increase in SC hydration of the forearm skin of healthy adults over a 2-week period and to compromise its water barrier function in a similar fashion. Systemic administration of high-dosage etretinate, 4 or 8 mg/kg/day, to guinea-pigs also induced dose-dependent increases in both SC hydration and TEWL measured on the plantar skin after 1 month. Moreover, in the animals given etretinate 4 mg/kg/day we confirmed a slight but significant decrease in the number of cell layers of the plantar SC. Likewise, patients with various dermatoses began to show similar functional changes of the SC in the uninvolved skin of the flexor surface of the forearms 3 weeks after the start of oral etretinate treatment, consisting of 50 mg daily for 2 weeks, followed by gradual dose tapering.(ABSTRACT TRUNCATED AT 250 WORDS)     

Standardized diaper care regimen: a prospective, randomized pilot study on skin barrier function and epidermal IL-1α in newborns

Adaptation of skin barrier function and interleukin-1α (IL-1α) content in diapered and nondiapered skin are poorly characterized in newborns receiving standard skin care. In a monocentric, prospective pilot study 44 healthy, full-term neonates were randomly assigned to skin care with baby wipes (n = 21) or water-moistened washcloth (n = 23) at each diaper change. Transepidermal water loss (TEWL), skin hydration, skin-pH, IL-1α, and epidermal desquamation were measured on days 2, 14, and 28 postpartum. Microbiological colonization was evaluated at baseline and on day 28. Significantly lower TEWL was found on the buttock in the group using baby wipes compared to water. IL-1α and skin hydration significantly increased and pH decreased independent of skin care regimen. IL-1α was significantly higher in diapered skin compared to nondiapered skin. Although skin care with wipes seems to stabilize TEWL better than using water, the skin condition and microbiological colonization were comparable using both cleansing procedures. Increase of epidermal IL-1α may reflect postnatal skin barrier maturation. These data suggest that neither of the two cleansing procedures harms skin barrier maturation within the first four weeks postpartum. Longer observations on larger populations could provide more insight into postnatal skin barrier maturation.     

Improvement in skin barrier function in patients with atopic dermatitis after treatment with a moisturizing cream (Canoderm)

Patients with atopic skin show a defective barrier function both in rough and in clinically normal skin, with an increasing risk of developing contact dermatitis. Moisturizing creams are often used in the treatment of dry skin. The purpose of this study was to investigate the influence of treatment with a urea-containing moisturizer on the barrier properties of atopic skin. Fifteen patients with atopic dermatitis treated one of their forearms twice daily for 20 days with a moisturizing cream. Skin capacitance and transepidermal water loss (TEWL) were measured at the start of the study and after 10 and 20 days. On day 21 the skin was exposed to sodium lauryl sulphate (SLS) and on day 22 the irritant reaction was measured non-invasively. Skin capacitance was significantly increased by the treatment, indicating increased skin hydration. The water barrier function, as reflected by TEWL values, tended to improve (P = 0.07), and the skin susceptibility to SLS was significantly reduced, as measured by TEWL and superficial skin blood flow (P < 0.05). Thus, it seems that certain moisturizers could improve skin barrier function in atopics and reduce skin susceptibility to irritants. The mechanism and the clinical relevance need further investigation.     

Effect of Aqueous Cream BP on human stratum corneum in vivo

Background Aqueous Cream BP is widely prescribed to patients with eczema to relieve skin dryness. The formulation contains sodium lauryl sulphate (SLS), a chemical that is a known skin irritant and a commonly used excipient in personal care and household products. The chronic effects of Aqueous Cream BP application on skin barrier function have not been determined. Objectives To characterize and assess skin barrier function of healthy skin after application of Aqueous Cream BP and to study the physical effects of the formulation on the stratum corneum (SC). Methods The left and right volar forearms of six human volunteers were each separated into treated and control sides. The treated sides of each forearm were subjected to twice daily applications of Aqueous Cream BP for 4 weeks at the end of which concomitant tape stripping and transepidermal water loss (TEWL) measurements were made. The untreated sides of the forearms were not exposed to any products containing SLS during the study period. Results Changes in SC thickness, baseline TEWL and rate of increase in TEWL during tape stripping were observed in skin treated with Aqueous Cream BP. The mean decrease in SC thickness was 1·1 μm (12%) (P = 0·0015) and the mean increase in baseline TEWL was 2·5 g m^?2 h^?1 (20%) (P < 0·0001). Reduced SC thickness and an increase in baseline TEWL, as well as a faster rate of increase in TEWL during tape stripping, were observed in 16 out of 27 treated skin sites. Conclusions The application of Aqueous Cream BP, containing ～1% SLS, reduced the SC thickness of healthy skin and increased its permeability to water loss. These observations call into question the continued use of this emollient on the already compromised barrier of eczematous skin.     

Specific barrier response profiles after experimentally induced skin irritation in vivo

Background

Recently, natural moisturizing factors (NMFs) and corneocyte surface topography were suggested as biomarkers for irritant dermatitis.

Objectives

To investigate how exposure to different irritants influences corneocyte surface topography, NMF levels and the barrier function of human skin in vivo.

Methods

Eight healthy adult volunteers were exposed to aqueous solutions of 60% n‐propanol, 0.5% sodium lauryl sulfate (SLS), 0.15% sodium hydroxide, and 2.0% acetic acid, and distilled water, in a repeated irritation test over a period of 96 hours. Erythema, transepidermal water loss (TEWL), skin hydration, the dermal texture index (DTI) and NMF levels were measured at baseline, and after 24 and 96 hours.

Results

SLS and sodium hydroxide had the most pronounced effects on erythema and TEWL. Although n‐propanol caused only slight changes in TEWL and erythema, it showed pronounced effects on skin hydration, NMF levels, and the DTI. NMF was the only parameter that was significantly altered by all investigated irritants. The changes in the DTI were inversely associated with NMF levels and skin hydration.

Conclusion

Skin barrier impairment and the inflammatory response are irritant‐specific, emphasizing the need for a multiparametric approach to the study of skin irritation. NMF levels seem to be the most sensitive parameter in detecting irritant‐induced skin barrier alterations.     

Validation of the VapoMeter, a closed unventilated chamber system to assess transepidermal water loss vs. the open chamber Tewameter®

BACKGROUND/AIM: Transepidermal water loss (TEWL) is one of the most important biophysical parameters for evaluating the efficiency of the human skin water barrier. Different approaches exist to measure TEWL. The most commonly used methodology consists of the open chamber diffusion technique in which the water vapor pressure gradient is measured in g/h m2 according to Fick's law. A typical apparatus is the Tewameter. Recently, a portable device--the VapoMeter--became available with a humidity sensor in a closed chamber. METHODS: In the present work, the closed chamber VapoMeter is compared with the open chamber Tewameter for its applicability to assess TEWL. A comparative study--including parallel in vivo measurements with both devices--was carried out on human forearm skin. RESULTS: It could be concluded that both instruments are reliable tools. A good correlation between recordings (r=0.503-0.966) was found with a consistent feature of measuring higher TEWL values for the Tewameter than for the VapoMeter. Probe pressure, probe temperature and relative humidity were revealed to be important parameters inducing significant differences in data outcome. CONCLUSIONS: From skin barrier damage experiments it became clear that the Tewameter is able to detect significantly smaller differences than the VapoMeter. In addition, the closed chamber device is currently not sensitive enough to discriminate for the effects induced by diurnal rhythm and fluctuations as a function of time. On the other hand, the small and handy VapoMeter allows more flexibility in measuring protocols and in in-use performance.     

Non‐invasive assessment of tryptophan fluorescence and confocal microscopy provide information on skin barrier repair dynamics beyond TEWL

The stratum corneum (SC) serves a primary function of skin barrier and understanding the kinetics of SC formation may provide great insight for skin diagnosis and evaluation of therapies. Besides trans‐epidermal water loss (TEWL), few methods have been characterized to assess skin barrier non‐invasively in vivo, particularly for dynamic measurements on the same specimen over time. The objective of this study was to characterize alternative non‐invasive methods to evaluate the dynamic processes involved in the recovery of normal human SC after total removal. TEWL, tryptophan fluorescence and reflectance confocal microscopy (RCM) were used to determine skin barrier function, cell turnover and epidermal morphology over a period of 10 days after total removal of the SC by tape stripping. The results show a biphasic recovery of TEWL over time, which contrasted with a linear increase of 2.3 μm/day in SC thickness. Tryptophan assessment of cell turnover also demonstrated a biphasic pattern attaining a maximum three to four times the levels of the control site 3 days after injury that slowly returned to baseline and displayed great correlation (R² > 0.95) to viable epidermis thickness that also achieved a maximum about 3 days after injury with an approximate increase of 55%. When plotting the change of TEWL versus SC thickness, a single exponential function is observed [Δ‐TEWL = 55 exp (?0.157×)] which contrasts with other proposed models. These methods were able to present rates for SC recovery processes beyond skin barrier (TEWL) that may provide new insights on kinetics of barrier formation for evaluation of skin conditions and treatments.