Skin irritant reactivity following experimental cumulative irritant contact dermatitis

Despite the frequency of irritant contact dermatitis, very little is known about the duration of barrier function impairment following cumulative irritant contact dermatitis. We studied post-irritation irritant reactivity by assessing the response to SLS irritation in previously irritated sites. Cumulative irritant contact dermatitis was induced on the forearms of 15 volunteers aged 18 to 50 years by repeated occluded application of 0.5% SLS I h per day over 3 weeks. 3, 6 and 9 weeks later, previously irritated and unirritated control sites were challenged with 2% SLS under occlusion for 23 h. Irritation was assessed by visual scoring, transepidermal water loss (TEWL) as an indicator of epidermal barrier function, and capacitance as a parameter of epidermal water content. While no difference in irritant reactivity between pre-irritated and unirritated sites was observed 3 weeks following irritant contact dermatitis, there was a significant hyporeactivity of previously irritated skin as expressed by clinical scores, TEWL and capacitance at 6 and 9 weeks. Our results indicate that epidermal barrier function remains altered even 9 weeks after cumulative irritant contact dermatitis. With regard to patch testing, post-irritation hyporeactivity might be a cause of false-negative tests on previously irritated sites.     

Sequential application of cold and sodium lauryl sulphate decreases irritation and barrier disruption in vivo in humans

BACKGROUND: Irritant contact dermatitis (ICD) is one of the most frequent types of occupational dermatitis. Different factors are involved in the development of contact dermatitis. In the food-processing industry, the combined exposure to different irritants may be involved in the development of ICD. Few data have been published regarding the irritant potential of sodium lauryl sulphate (SLS) in combination with cold. OBJECTIVES: The present study was intended to analyse whether cold exposure and low skin temperature influence the development of ICD. METHODS: Twenty (part I) and 12 (part II) healthy volunteers were exposed twice daily for 4 days to SLS alone, different low temperatures alone (4 degrees C six times for 90 s with an interval of 20 s or 15 degrees C for 10 min) or a combination of cold and SLS (19.6 microL SLS 1% cm(-2), part I; or 52.6 microL SLS 0.5% cm(-2), part II) using the tandem repetitive irritation test. Irritant cutaneous reactions were measured by noninvasive biophysical methods with transepidermal water loss as a parameter for permeability barrier function and skin colour reflectance together with visual scoring as parameters for inflammatory reactions. RESULTS: Cold alone caused no significant skin reaction compared with untreated control. Exposure to SLS alone and SLS together with cold (independent of the applied temperature of 4 or 15 degrees C) twice daily induced a clear irritant reaction and barrier disturbance. Reactions did not differ whether SLS was applied before or after cold. Furthermore, 'tandem application' of cold and SLS diminished the barrier disruption and irritant reaction compared with SLS alone. CONCLUSIONS: We conclude that the application of cold may have a protective effect on the development of ICD, at least in our short-term model.     

Effect of an antioxidant (quercetin) on sodium-lauryl-sulfate-induced skin irritation

Quercetin is a bioflavonoid with antioxidant and anti-inflammatory activity. The purpose of this study was to examine the effect of quercetin on acute skin irritation, with special interest in the skin barrier function recovery. Acute irritant contact dermatitis was induced in 15 patients by 24-h occlusion of 2% sodium lauryl sulfate (SLS) (day (D) 1). The influence of application on SLS-irritated skin of topical quercetin for 5 consecutive Ds, compared to vehicle and controls, was studied. Parameters measured were transepidermal water loss (TEWL) and erythema index. Final measurements were taken on D 7 after a 1-D rest period. TEWL and the erythema index continued to rise 2 D after application of SLS and 1 D after treatment with quercetin, vehicle or controls. Both TEWL and erythema values at D 7 did not return to values before the SLS barrier disruption at all the test sites. Therefore, quercetin topically applied after induction of irritant contact dermatitis does not appear to increase the recovery of barrier function and erythema caused by SLS.     

Effect of barrier perturbation on cutaneous salicylic acid penetration in human skin: in vivo pharmacokinetics using microdialysis and non-invasive quantification of barrier function

We have used microdialysis in the dermis for assessing penetration kinetics of salicylic acid (SA) in healthy volunteers (n = 18), following application on the volar aspect of the left forearm. Penetration was monitored at four locations: in normal (unmodified) skin and in skin with perturbed barrier function from (i) repeated tape stripping (ii) irritant dermatitis from 1 or 2% sodium lauryl sulphate (SLS) for 24 h and (iii) delipidization by acetone. The order of the treatments was randomized according to a latin square design. Epidermal barrier function and skin irritation were assessed in each location using evaporimetry and colorimetry. Transepidermal water loss (TEWL) values confirmed that both mild (acetone), moderate (1% SLS) and severe barrier damage (tape stripping and 2% SLS) had occurred. Microdialysis sampling with two parallel probes in the dermis was performed in each of the four treatment areas for every subject. SA (5% in ethanol) was applied in a chamber glued to the skin overlying the microdialysis probes and sampling was continued for 4 h. SA was detectable in all samples and measurable in all samples from penetration through perturbed skin. Comparing the SA penetration in barrier-perturbed skin with the penetration in unmodified skin in the same subject, the mean SA penetration increase was 2.2-fold in acetone-treated skin (P = 0.012), 46-fold in mild dermatitis and 146- and 157-fold in severe dermatitis and tape stripped skin, respectively (P < 0.001). The penetration of SA significantly correlated with the measurements of barrier perturbation by TEWL (P = 0.01) and erythema (P = 0.02) for each individual. Microdialysis sampling of SA penetration was more sensitive than non-invasive measuring techniques in detecting significant barrier perturbation in acetone-treated skin. A positive dose-response relationship for the percutaneous penetration of SA in response to increasing SLS pretreatment concentrations and thus the degree of irritant dermatitis was found. When analysing data by location on the forearm, a tendency towards an intraregional variation in the reactivity to barrier damage was found, with the most proximal location displaying higher reactivity scores than the most distal location in response to the same barrier perturbation procedures. The penetration of SA was not significantly different between locations. In conclusion, using microdialysis in the dermis to obtain real-time dermal pharmacokinetics in the target organ, this study demonstrates highly increased and differentiated cutaneous penetration of SA in barrier-perturbed skin. The measured drug penetration was demonstrated to correlate with non-invasive quantification of barrier damage.     

Abnormal epidermal barrier in the pathogenesis of contact dermatitis

A crucial role of the epidermal permeability barrier is obvious in contact dermatitis. An intact skin barrier prevents the penetration of harmful substances into the skin. Irritants and allergens that stay on the skin surface and come into contact with the stratum corneum only do not harm the skin. After disruption of the skin barrier, however, irritants may penetrate into the living epidermal layers, injure the keratinocyte membrane, and release cytokines, which leads to inflammation and to irritant contact dermatitis. The skin barrier is often disrupted by chronic exposure to water plus detergents, solvents, or other irritants. A disrupted barrier in irritant contact dermatitis also allows for the penetration of allergens. Allergens may come into contact with Langerhans and T cells, induce immunological reactions, and cause inflammation, which results in allergic contact dermatitis. Treatments in contact dermatitis should restore the skin barrier to prevent relapse of the disease. Topical corticosteroids, most often used in treating contact dermatitis, reduce immunological reactions and inflammation but do not lead to a complete barrier repair. Skin barrier repair is more complete after treatment with calcineurin inhibitors and bland lipid-based emollient; therefore, these preparations should be preferred for long-term treatment of contact dermatitis.     

Nonanoic acid--an experimental irritant

Irritant contact dermatitis is defined as a non-immunological skin reaction following exposure to various chemical, mechanical and physical factors. It is known that the skin response to irritants depends on the irritant applied and differs between chemically different irritants. Sodium lauryl sulfate (SLS) is an anionic detergent and the most frequently used substance in experimental irritant contact dermatitis. In 1980, it was suggested that nonanoic acid (NNA) could be used as a positive control when patch testing. Since then, NNA has been used as an experimental irritant in several studies and has been used as a chemically different substance compared to SLS. The present article presents a review of the application of NNA in studies on skin irritancy and experimental irritant contact dermatitis.     

Effect of sodium lauryl sulfate-induced skin irritation on in vivo percutaneous penetration of four drugs.

The influence of sodium lauryl sulfate-induced irritant contact dermatitis on in vivo percutaneous penetration was investigated for four 14C-labeled compounds with diverse physicochemical properties: hydrocortisone (HC), indomethacin (IM), ibuprofen (IB), and acitretin (AC). Hairless guinea pigs were pretreated for 24 h with either 0.5% sodium lauryl sulfate (SLS) to induce irritant contact dermatitis or with water (controls). Twenty-four hours after pretreatment, 450 microliters saturated solutions of HC, IM, IB, or AC in isopropylmyristate were applied to the pretreated skin for 24 h. Systemic absorption was determined by urinary and fecal excretion of compounds. Drug concentrations in stratum corneum (obtained by tape cellophane stripping after decontamination of the application site) and in epidermis/dermis (punch biopsy) were also investigated. Systemic absorption of topically applied drugs (as evaluated by urinary and fecal excretion) in SLS-irritated skin was significantly increased for HC (factor 2.6) followed by IB (1.9 times) and IM (1.6 times) but not increased for AC. However, drug concentrations in the viable epidermis and dermis were 70% lower in SLS-irritated than normal skin for HC, but not different for IB, IM, and AC. Thus, the influence of the state of the skin (irritant dermatitis versus healthy) on percutaneous penetration was different for diverse drugs. The general assumption that percutaneous penetration and drug tissue concentrations were higher in diseased versus healthy skin was not found to be true in our irritated-skin model.     

Fruit acids do not enhance sodium lauryl sulphate-induced cumulative irritant contact dermatitis in vivo

Combined exposure to different irritants in the workplace may lead to irritant contact dermatitis, which is the main type of occupational dermatitis among bakers and confectioners. Following previous work on "tandem irritation", a panel of healthy volunteers was exposed twice daily for 4 days to the organic fruit acids: citric, malic, and lactic acid, either alone or in tandem application with 0.5% sodium lauryl sulphate (SLS) in a repetitive irritation test. Irritant cutaneous reactions were quantified by visual scoring and non-invasive measurement of transepidermal water loss and skin colour reflectance. Twice daily application of either citric or malic acid alone did not induce a significant irritant reaction. Combined exposure to one of the fruit acids and SLS caused marked barrier disturbance, but the latter irritant effect was smaller than that obtained by combined exposure to SLS and water. Thus, combined exposure to the above-mentioned fruit acids and SLS did not enhance cumulative skin irritation.     

Fruit acids and sodium hydroxide in the food industry and their combined effect with sodium lauryl sulphate: controlled in vivo tandem irritation study

BACKGROUND: Cutaneous exposure to a variety of irritants has been extensively studied in recent years. Nevertheless, knowledge of the induction of irritant dermatitis, especially by mild irritants at low doses and for a short duration of exposure, is still incomplete. OBJECTIVES: To quantify the irritant effects and barrier disruption properties of ascorbic acid (ASC), acetic acid (ACA) and sodium hydroxide (NaOH), particularly in combination with an anionic detergent, sodium lauryl sulphate (SLS). METHODS: In a tandem repeated irritation test, the irritants were applied for 30 min twice daily for 4 days to the skin of the mid-back of 19 healthy volunteers of both sexes. We used bioengineering techniques for measurement of transepidermal water loss (TEWL) and skin colour reflectance, as well as visual scoring. RESULTS: Repeated application of ASC and ACA caused a moderate increase in TEWL and erythema. The sequential application of ASC or ACA and SLS enhanced these effects. NaOH induced a strong reaction when applied both occlusively and nonocclusively as well as in combination with SLS, with an early onset of the inflammatory signs, leading to discontinuation of the application on the third day in most of the test fields. Notably, the irritant effect of NaOH was not as marked when applied sequentially with SLS. CONCLUSIONS: Our results demonstrate that concurrent application of an anionic detergent and a mild acidic irritant can lead to disruption of the barrier function which, although not additive, is still considerable. The combined application of SLS and mild acids does not prevent SLS-induced irritation. Furthermore, we showed that NaOH in low concentrations may also act as a potent irritant but that its effect is not enhanced by SLS. The necessity of adequate skin protection and reduction of contact with substances that are potentially barrier disruptive and irritant, e.g. in the food industry, is emphasized, not only when handling detergents, but also when processing food products.     

The effect of irritant dermatitis on cutaneous bioavailability of a metronidazole formulation, investigated by microdialysis and dermatopharmacokinetic method

Background:  Determination of drug penetration in diseased skin represents a challenge.
Objective:  To compare dermal microdialysis and tape-strip sampling of drug penetration in normal skin and skin with irritant dermatitis.
Methods:  The two methodologies were employed simultaneously in 16 healthy volunteers. Samples were collected in a study of the penetration of a metronidazole cream formulation (Flagyl^® 1%) applied to forearm skin in both areas with irritant dermatitis and normal skin. Barrier perturbation and the depth of microdialysis probes were quantified by non-invasive bioengineering methods.
Results:  Microdialysis showed a significant threefold increase in metronidazole penetration in skin with irritant dermatitis compared with unmodified skin. Conversely, the concentration of metronidazole in tape-strip samples was significantly decreased in irritant dermatitis.
Conclusion:  The selection of sampling methodology should be based on the skin layer of interest as well as the integrity of the skin barrier. Whenever the dermal tissue is the target for topical treatment, microdialysis sampling should be the method of choice.     

Beneficial effects of a skin tolerance-tested moisturizing cream on the barrier function in experimentally-elicited irritant and allergic contact dermatitis

In experimentally-induced irritant (ICD) and allergic (ACD) contact dermatitis, an oil-in-water (o/w) cream was applied to investigate its effects on a disturbed barrier function compared to untreated physiological barrier repair. Transepidermal water loss (TEWL) measurements were performed. Before the start of the experiments, the skin tolerance of the cream was examined, revealing the non-irritating characteristics of the ingredients and the absence of any contact allergic patch test reaction. In the ICD study, sodium lauryl sulfate (SLS) patches were applied to the forearms of young female volunteers. Consequently, it was observed that repeated cream application (14 days, 2x/day) significantly improved the TEWL of SLS-damaged skin, leading to a complete recovery on day 15. In the ACD study, disruption of skin barrier function was obtained by a nickel-mediated contact allergy patch (CAP) test. The cream was then applied 2x/day for 4 consecutive days. Assessment of TEWL clearly showed that recovery of the disrupted skin significantly improved after cream application in comparison to untreated barrier repair.     

Effect of sodium lauryl sulfate-induced skin irritation on in vitro percutaneous absorption of four drugs.

The influence of irritant contact dermatitis on percutaneous penetration was investigated for four 14C-labeled compounds with diverse physicochemical properties: hydrocortisone (HC), indomethacin (IM), ibuprofen (IB), and acitretin (AC). Hairless guinea pigs were pretreated in vivo for 24 h with either 0.5% sodium lauryl sulfate (SLS) to induce irritant contact dermatitis or with water (controls). Twenty-four hours after pretreatment animals were sacrificed. Percutaneous penetration was then measured using in vitro diffusion cells and the removed (pretreated) skin. The following parameters were determined: cumulative amount of compound penetrated, steady state flux, lag time, and permeability coefficient, skin concentration per unit area, and the relative amount of drug remaining in the skin (as a percentage of the cumulative amount of compound penetrated through the skin). SLS pretreatment resulted in moderate irritant dermatitis in all animals and increased in vivo transepidermal water loss 4.5 times. Flux was increased in SLS-pretreated skin as compared with controls for all four compounds, with the greatest enhancement for hydrocortisone (HC) (5.9 times), followed by indomethacin (IM) (4.6 times), ibuprofen (IB) (3.9 times), and acitretin (AC) (3.4 times). Skin concentrations increased to a smaller degree from 1.6 times (IB) and 2.6 times (HC) to 3.4 times (IM). However, AC skin concentrations were not different between the two groups. Thus, percutaneous penetration parameters were equivocally influenced by SLS-induced irritation. Increased skin concentrations were paralleled by even higher increases in flux.     

Sodium lauryl sulfate (SLS) induced irritant contact dermatitis: a correlation study between ceramides and in vivo parameters of irritation

Sodium lauryl sulfate (SLS), a surfactant frequently used in the induction of experimental irritant contact dermatitis in animals and in humans, characterstically induces a dose-related increase in TEWL (transepidermal water loss). Ceramides are considered to be important in the regulation of the skin barrier. We therefore examined the relationship between initial ceramide content of stratum corneum and induced changes in skin color (erythema) and barrier function, after SLS application under occlusion (1% and 3% in water) to the forearm of 14 volunteers. Stratum corneum sheets were removed, stratum corneum lipids extracted, and ceramide composition determined from chromatograms (TLC) using densitometry. After determining baseline skin color and TEWL at each area. 2 samples of stratum corneum were obtained from each volunteer. Clinical and instrumental controls of the SLS-induced irritation were performed at 24, 48, 72 and 96 h. Erythema was evaluated by colorimetry; barrier impairment by changes in TEWL. We found inverse correlations between baseline ceramide 61 (weight) and the 24 h erythema score for SLS: between ceramide I and 24 h TEWL, and between ceramide 611 and 72 h TEWL for SLS 3%. Our findings suggest that low levels of these ceramides may determine a proclivity to SLS-induced irritant contact dermatitis.     

Barrier recovery and influence of irritant stimuli in skin treated with a moisturizing cream

Moisturizers are used daily by many people to alleviate symptoms of clinically and subjectively dry skin. Recent studies suggest that certain ingredients in creams may accelerate the recovery of a disrupted barrier and decrease the skin susceptibility to irritant stimuli. In the present single-blind study, a moisturizing cream was tested for its influence both on barrier recovery in surfuctant-damaged skin and on the susceptibility of normal skin to exposure to the irritant sodium lauryl sulphate (SLS). Parameters measured were transepidermal water loss (TEWL) and skin corneometer values, indicating degree of hydration. Treatment of surfactant-damaged skin with the test cream for 14 days promoted barrier recovery, as observed as a decrease in TEWL. Skin corneometer values also normalized more rapidly during the treatment. In normal skin, use or the test cream significantly reduced TFWL after 14 days of treatment, and irritant reactions to SLS were, significantly decreased. Skin corneometer values increased after only 1 application and remained elevated after 14 days. In conclusion, the accelerated rate of recovery of surfactant-damaged skin and the lower degree of SLS-induced irritation in normal skin treated with the test cream may be of clinical relevance in attempts to reduce contact dermatitis due to irritant stimuli.     

Assessment of skin irritancy by 2 short tests compared to acute irritation induced by sodium lauryl sulfate

Irritant contact dermatitis is a very common disease that i. preventable by protective measures The development of screening methods to identify subject with increased susceptibility in irritants is essential in reduce the incidence of this disorder in the workplace On the outlook for such methods. 2 quick non-invasive tests for irritability of the skin were compared to reliable, but time-consuming, patch testing with sodium lauryl sulfate (SLS) In 20 healthy volunteers, 0.5% SLS was applied on the medial 1/3 of the forearm for 23 h in order to induce experimental irritant contact dermatitis. On the same part of the forearm, 3 concentrations of dimethylsulfoxide (DMSO) and a solution of 0.2 mol/1 NaOH were applied for 5 min. Assessment of skin irritability was made by visual scoring and measurement of transepidermal water loss. No correlation between the "Quick tests" and SLS patch testing was found, indicating that tests assess different mechanisms of irritation.     

The tandem repeated irritation test: a new method to assess prevention of irritant combination damage to the skin

The effect of a protective cream was tested in a new tandem repeated irritation test with tandem application of 0.5% sodium lauryl sulphate (SLS) and undiluted toluene. The irritants were applied twice daily for 30 min to the ventral forearms of 20 volunteers. Irritant cutaneous reactions were quantified by a visual score, transepidermal water loss, chromametry and skin capacitance. Concurrent application of SLS/toluene induced stronger reactions than those caused by twice daily application of each irritant on its own. A protective effect of the protective cream was obtained against all treatment combinations and was significant for SLS/SLS (p < or = 0.01) and SLS/ toluene (p < or = 0.05). Our results indicate that the tandem repetitive irritation test has great potential in the evaluation of skin care products to prevent irritant contact dermatitis.     

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.     

Pathological findings in cumulative irritation induced by SLS and croton oil in hairless mice

It is known that the pathological features of acute irritant contact dermatitis are specific according to the irritant. However, in chronic irritant contact dermatitis, it is not clear whether specific patterns exist. To investigate whether the specific pathology of acute irritant contact dermatitis is sustained in chronic irritant contact dermatitis, sodium lauryl sulfate (SLS) and croton oil were applied 3x a week for 2 weeks on the dorsal skin of hairless mice using Finn Chambers. The pathologic changes induced by irritants at various concentrations were evaluated using H&E and Luna's staining, as well as immunohistochemistry for 5-bromo-2-deoxyuridine (BrdU), keratin 6 and loricrin. Our results showed that epidermal hyperplasia and inflammatory infiltration were relatively marked in the groups treated with higher concentrations of irritants. These features were more prominent in the 1% croton oil treated group than in the 0.25% SLS treated group. However, lower concentrations of irritants resulted in very similar histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical. Our results suggest that the histological responses to irritants vary with concentration in cumulative irritation, as in acute irritation, but repetitive mild irritation may evoke common histological changes, characterized by epidermal hyperplasia with minimal inflammatory infiltration, irrespective of the chemical used.     

Air flow at different temperatures increases sodium lauryl sulphate-induced barrier disruption and irritation in vivo

BACKGROUND: Combined exposure to dry climatic conditions and local heat sources together with detergents represents a common workplace situation. These conditions may support the induction of chronic barrier disruption leading subsequently to irritant contact dermatitis (ICD). OBJECTIVES: To test the irritant and barrier disrupting properties of air flow at different temperatures and velocities. METHODS: Using noninvasive biophysical measurements such as transepidermal water loss (TEWL) (TM 210; Courage & Khazaka, Cologne, Germany) we assessed the effects of short-term exposure to air flow at different temperatures (24 degrees C and 43 degrees C) in combination with sodium lauryl sulphate (SLS) 0.5% on the skin of 20 healthy volunteers in a tandem repeated irritation test. Chromametry was used to control the accuracy of the SLS irritation model. RESULTS: In our study air flow alone did not lead to a significant increase in TEWL values. Sequential treatment with air flow and SLS led to an impairment of barrier function and irritation stronger than that produced by SLS alone. The two different air flow temperatures led to different skin temperatures but had no influence on permeability barrier function. CONCLUSIONS: Warm air flow has an additional effect on the SLS-induced barrier disruption in a tandem irritation test with sequential exposure to SLS/air flow. This combination is suspected to promote ICD in workplace and household situations, especially in short-term applications as tested in our model.     

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.