Skin permeability barrier and occlusion: no delay of repair in irritated human skin

Evaluating the Irritant Factors of Silicone and Hydrocolloid Skin Contact Adhesives Using Trans-Epidermal Water Loss, Protein Stripping, Erythema, and Ease of Removal

A composite silicone skin adhesive material was designed to improve its water vapor permeability to offer advantages to wearer comfort compared to existing skin adhesive dressings available (including perforated silicone and hydrocolloid products). The chemical and mechanical properties of this novel dressing were analyzed to show that it has a high creep compliance, offering anisotropic elasticity that is likely to place less stress on the skin. A participant study was carried out in which 31 participants wore a novel silicone skin adhesive (Sil2) and a hydrocolloid competitor and were monitored for physiological response to the dressings. Trans-epidermal water loss (TEWL) was measured pre- and postwear to determine impairment of skin barrier function. Sil2 exhibited a higher vapor permeability than the hydrocolloid dressings during wear. Peel strength measurements and dye counter staining of the removed dressings showed that the hydrocolloid had a higher adhesion to the participants' skin, resulting in a greater removal of proteins from the stratum corneum and a higher pain rating from participants on removal. Once the dressings were removed, TEWL of the participants skin beneath the Sil2 was close to normal in comparison to the hydrocolloid dressings that showed an increase in skin TEWL, indicating that the skin had been highly occluded. Analysis of the skin immediately after removal showed a higher incidence of erythema following application of hydrocolloid dressings (>60%) compared to Sil2, (<30%). In summary, this modified silicone formulation demonstrates superior skin protection properties compared to hydrocolloid dressings and is more suitable for use as a skin adhesive.

Investigation of Cannabinoid Acid/Cyclodextrin Inclusion Complex for Improving Physicochemical and Biological Performance

This study aimed to investigate the enhancement of cannabinoid acid solubility and stability through the formation of a cannabinoid acid/cyclodextrin (CD) inclusion complex. Two cannabinoid acids, tetrahydro-cannabinolic acid (THCA) and cannabidiolic acid (CBDA), were selected as a model drug along with five types of CD: α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and methylated-β-cyclodextrin (M-β-CD). Phase solubility studies were conducted using various types of CD to determine the complex stoichiometry. The preparation methods of the CD inclusion complex were optimized by adjusting the loading pH solution and the drying processes (spray-drying, freeze-drying, spray-freeze-drying). The drying process of the cannabinoid acid/M-β-CD inclusion complex was further optimized through the spray-freeze-drying method. These CD complexes were characterized using solubility determination, differential scanning calorimetry (DSC), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and 1H NMR spectroscopy. DSC, XRD, and FE-SEM studies confirmed the non-crystalline state of the cannabinoid acid/CD inclusion complex. The permeation of THCA or CBDA from the M-β-CD spray-freeze-dried inclusion complex was highly improved compared to those of cannabis ethanolic extracts under simulated physiological conditions. The stability of the cannabinoid acid/M-β-CD inclusion complex was maintained for 7 days in a simulated physiological condition. Furthermore, the minimum inhibitory concentration of cannabinoid acid/M-β-CD inclusion complex had superior anti-cancer activity in MCF-7 breast cancer cell lines compared to cannabinoid acid alone. The improved physicochemical and biological performances indicated that these CD inclusion complexes could provide a promising option for loading lipophilic cannabinoids in cannabis-derived drug products.

Effects of impermeable and semipermeable glove materials on resolution of inflammation and epidermal barrier impairment after experimental skin irritation

BACKGROUND

Semipermeable membranes might be suitable for glove liners or comfort gloves in individuals with irritant contact dermatitis (ICD).

OBJECTIVES

To evaluate the effects of different glove materials on inflammation and epidermal barrier impairment after experimental skin irritation.

METHODS

Nine test areas on the volar forearms of 24 healthy volunteers were irritated with sodium lauryl sulfate (1%) and afterward covered for 6 days (6 or 8 h/day) with semipermeable Sympatex (SYM), vinyl (OCC), combinations of vinyl with Sympatex (SYM/OCC) or cotton (COT/OCC), or left uncovered (CON). Up to day 10, measurements of transepidermal water loss (TEWL), erythema (a*), skin humidity (SH) and visual scoring (VS) were applied.

RESULTS

No significant differences in skin parameters were found between COT/OCC and SYM/OCC as well as between each of the combinations and CON. SYM, COT/OCC and SYM/OCC led to better results for most skin parameters than OCC alone.

CONCLUSIONS

Occlusive material has a negative impact on skin barrier recovery and inflammation after skin irritation whereas SYM is not inferior to uncovered areas indicating good tolerability. Altogether, the data suggest that SYM is a useful alternative to COT as material for glove liners and comfort gloves in ICD patients.

Secretome of human umbilical cord mesenchymal stem cell maintains skin homeostasis by regulating multiple skin physiological function

Skin is the largest organ in the body and the first defense to resist various diseases and external stimuli that easily cause infection and inflammation. Aseptic inflammation, barrier damage, and foreign aid pressure induce the destruction and damage to the skin microenvironment. Subsequently, it destroys the skin's physiological function, leading to the maintenance and circulation of steady-state imbalance and aggravating the process of skin disorders. Our study evaluated the therapeutic potential of the secretome of human umbilical cord mesenchymal stem cells (UC-CM) for dermatological diseases in adult human skin cells, ex vivo skin tissue, and a 3D skin model. Our data suggested several advantages of UC-CM due to (1) their low cytotoxicity and sensitization properties; (2) their anti-inflammatory capacity for treating inflammatory chronic cutaneous diseases; (3) their enhanced capacity of the skin barrier for treating abnormal barrier metabolism; and (4) their positive impact on restoring skin homeostasis due to effective regulation ability of skin physiological function including cell apoptosis, detoxification, and anti-aging. We thus envisage that the possibility of harnessing the therapeutic potential of UC-CM might benefit patients suffering from inflammatory skin disorders such as atopic dermatitis, acne, and psoriasis.

Acceptance of semipermeable glove liners compared to cotton glove liners in health care workers with work-related skin diseases: Results of a quasi-randomized trial under real workplace conditions

BACKGROUND

Glove liners (GLs) made of cotton (COT) are worn under impermeable gloves to prevent occlusion effects. Semipermeable GLs made of Sympatex (SYM) might be an alternative.

OBJECTIVES

To evaluate the acceptance of GLs (COT/SYM) in health care workers (HCWs) with work-related skin diseases (WRSDs).

METHODS

One hundred sixty-one HCWs with WRSDs were asked to wear GLs in combination with occlusive gloves for 10 ±2 weeks under workplace conditions. A questionnaire was applied to compare acceptance and usability of the respective glove combinations and previously used protective gloves (PUGs).

RESULTS

A total of 120 data sets were available (SYM: n = 65, 77.4%; COT: n = 55, 71.4%). Both GLs provided a significantly lower sweating sensation, more pleasant climate, comfortable wearing experience, and moist or dry feeling on the skin compared to PUGs. SYM-GLs performed significantly better than COT-GLs regarding mobility of hands, sensitivity, and sense of touch. COT-GLs were significantly better than SYM-GLs in the categories fit, donning and doffing, and material contact.

CONCLUSIONS

Both GLs did not impair work performance, were applicable in various areas of health care activities, and were preferred over PUGs. Our results indicate that SYM-GLs are an alternative to COT-GLs and thus may contribute to current prevention strategies.

Enhanced expression and secretion of antimicrobial peptides in atopic dermatitis and after superficial skin injury

Human skin can defend itself against potentially invading microorganisms by production of antimicrobial peptides (AMPs). The expression of AMPs in atopic dermatitis (AD) is still emerging. To gain more insight into the role of AMPs in AD, we systematically analyzed the expression of ribonuclease 7 (RNase 7), psoriasin, and human beta-defensins (hBD)-2 and -3 in AD compared with psoriatic and healthy control skin as well as after experimental barrier disruption. Immunostaining revealed enhanced expression of all AMPs in the lesional skin of untreated AD and psoriasis when compared with non-lesional skin and controls. Accordingly, induced in vivo secretion of RNase 7, psoriasin, and hBD-2 was detected using ELISA on lesional skin in AD and in even higher concentrations in psoriasis. The secretion of AMPs did not correlate with severity of AD and Staphylococcus aureus colonization. Skin barrier disruption caused enhanced immunoreactivity of hBD-2 and hBD-3 after 24 hours. Strong secretion of RNase 7 was already detected after 1 hour, whereas hBD-2 secretion was significantly enhanced after 24 hours only under occlusion. Thus, a disturbed skin barrier may trigger AMP induction in AD and psoriasis. The functional role of AMP in AD, especially with regard to the control of S. aureus colonization, needs further analysis.

Basistherapie der Psoriasis vulgaris

Maintenance therapy in the interval between flares is an essential part of the therapeutic approach to psoriasis. The therapeutic effectiveness of maintenance therapy results from a positive influence on the physicochemical characteristics of individual compartments of the skin, especially the stratum corneum and the epidermis. The objective is revert from a pathological milieu toward a physiological one. These effects may be supplemented by pharmacological or biochemical effects of the active substances or substance mixtures. Focal points are the use of lipophilic bases as well as keratoplastic, antiseptic and antipruriginous additives.

Artificial disruption of skin barrier prior to irritant patch testing does not improve test design

BACKGROUND

Irritant patch testing is often performed as a 24- or 48-h occlusive patch test with low concentrations of sodium lauryl sulphate (SLS).

OBJECTIVES

The aim of this study was to investigate potential ways to shorten this test procedure and obtain precise test results.

PATIENTS AND METHODS

Thirty-six healthy volunteers underwent irritant patch testing with different pretreatments (PT) of the test fields. Occlusive test chambers were applied on the upper back with SLS 0.5%, 1%, 2% and 5% in large Finn Chambers(R). The patches were removed after 4 and 24 h, respectively, depending on the concentration used. Test fields were pretreated as follows: PT 0, field without any PT (control); PT 1, prick with lancet; PT 2, prick with test stamp; PT 3, scratch with lancet; PT 4, incision with standardized incision instrument (0.1-0.2 mm depth). Skin reactions were evaluated by transepidermal water loss (TEWL), skin erythema and skin hydration and as well by a visual score (VS) at 4, 24 and 72 h.

RESULTS

Our data show an obvious distinction between PT 0-2 and PT 3-4 at all measurement methods. The average TEWL values with PT 3-4 were higher than those with PT 0-2, especially on the 4-h course. This distinction may derive from the shape and size of the skin impairment achieved by PT 3-4, leading to a mechanical barrier disruption. However, SLS may infiltrate directly into deeper skin layers supported by capillarity. Consequently, no or little penetration through the epidermis and interaction with its structures occurs, which is responsible for irritant skin reactions. The SLS dose in the upper skin layers is therefore lower at these PTs. The lower remaining dose of SLS also explains this distinction, especially for the VS. Additionally, there are presumed reactions in deeper layers of the epidermis and dermis at PT 3-4.

CONCLUSIONS

In summary, all data suggest a different reaction pattern from the classical irritant response. Therefore, application without any PT seems to be best suited for irritancy skin testing, especially for visual assessment. PTs prior to irritant patch testing have been shown to be unjustifiable.

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

Effects of skin occlusion in patch testing with sodium lauryl sulphate

BACKGROUND

When evaluating transepidermal water loss (TEWL) in patch testing, the occlusive effect of the patch must be considered as an important artificial impairment of the measurement.

OBJECTIVES

To investigate the time course of effects of occlusion.

METHODS

Epicutaneous patches with sodium lauryl sulphate (SLS) 0.25%, SLS 0.5%, water and an empty test chamber (control) were applied on the volar forearm for different time intervals (12, 24, 48 h). Test reactions were evaluated by measurement of TEWL immediately, every 15 min during the first hour, every 30 min during the following 3 h and 24 h after patch removal.

RESULTS

After patch removal, TEWL values showed a steep increase. When compared with basal values, TEWL values after SLS patch testing remained increased for 24 h, whereas TEWL values on water patch sites were only significantly increased for up to 180 min, and on empty patch sites for only up to 120 min after patch removal. The prolonged increase in TEWL values in SLS patch testing seemed to be induced by barrier function damage caused by SLS itself, as shown in various earlier studies. After the initial increase, TEWL values showed a significant decrease for all patches from 0 to 120 min after patch removal. Patch testing with water gave a significant decrease in TEWL values up to 180 min, and for empty chambers (control) up to 150 min after removal of patches. These data suggest that the occlusive effect on TEWL in patch testing ends 3 h after the removal of test chambers.

CONCLUSIONS

We recommend TEWL measurement in SLS patch testing after a period of at least 3 h after patch removal. For practical purposes a 24-h period after patch removal may be useful.

Skin protection programmes

Educational programmes, including evidence-based recommendations on skin protection (skin protection programmes), have been proposed for the prevention of irritant contact dermatitis in occupations with a high frequency of this disease. Recent intervention studies directed at wet-work employees showed a positive influence on wet-work behaviour and on clinical skin symptoms. The structure and implementation of skin protection programmes are discussed.

Effect of skin barrier competence on SLS and water-induced IL-1alpha expression

For screening of a potential irritant it is essential that an early marker for irritation should be chosen which could be detected before the physiological signs of irritation occur. Interleukin 1 alpha (IL-1alpha) is widely accepted as such a marker in both in vivo and in vitro test systems. In this study, we have determined the mRNA levels of IL-1alpha in the epidermis after topical application of sodium dodecyl sulphate (SLS) in both a commercially available epidermal kit (EpiDerm) and in excised skin. Furthermore, we have determined the effect of water, the vehicle for SLS, on IL-1alpha mRNA levels. Topical application of water to excised skin increases IL-1alpha mRNA levels sixfold in the epidermis whereas topical application of water to EpiDerm cultures did not alter IL-1alpha mRNA levels. This is explained by the finding that EpiDerm cultures have a sub-optimal barrier function when compared with excised skin - topical application of SLS was clearly toxic at much lower concentrations in EpiDerm cultures (0.2% SLS) than in excised skin (5% SLS). Also caffeine penetration was 10-fold higher through EpiDerm cultures than through the excised skin. Therefore, incubation of control EpiDerm cultures at 100% humidity effectively mimics topical exposure to water. An additional increase in IL-1alpha mRNA levels observed between topical application of water and SLS is similar (about threefold) in both experimental systems. In conclusion, in vitro reconstructed epidermis models, such as EpiDerm, can be used as a predictive model for irritancy screening. However, great care should be taken when interpreting the results due to the fact that EpiDerm cultures do not have a competent barrier function and therefore lower irritant concentrations are required than in in vivo or ex vivo studies in order to induce cytotoxic effects. Furthermore, the irritant effects of the vehicle should not be neglected. Our results show clearly that the topical application of water to excised skin results in increased levels of IL-1alpha mRNA in the epidermis. This is a cytokine that is widely used as an early marker for skin irritation.

Occlusive properties of monolayer patches: in vitro and in vivo evaluation

PURPOSE

Patches can cause a different grade of skin occlusion, depending on matrix composition and thickness, backing layer material. The aim of this work was to verify if in vitro water vapour permeability (WVP) values are predictive of transepidermal water loss (TEWL) and Fourier-transform infrared (FTIR) spectroscopy values measured in vivo after 24 h of methacrylic or acrylic monolayer patches application. The correlation between both in vivo methods has been evaluated.

METHODS

The WVP, TEWL and FTIR measurements were performed by using four patches made of a methacrylic or an acrylic polymeric system (250 and 500 microm thickness on a polyurethane backing layer). A fifth patch was made of the methacrylic matrix on a polvvinyl chloride backing layer. RESULTS. A good correlation was found between TEWL values and IR water/lipid absorbance ratios. The in vitro WVP values are in a good correlation with the results of both in vivo methods: TEWL = -().()WVP + 21.31 (R2 = 0.9312): FTIR water/lipid ratio = -0.01WVP + 27.15 (R2 = 0.9447).

CONCLUSIONS

The in vitro method proposed for measuring the WVP is predictive of the degree of occlusion resulting from the in vivo application of monolayer patches.

Locobase repair cream following CO2 laser skin resurfacing reduces interstitial fluid oozing

BACKGROUND

The cosmetic result after laser resurfacing depends not only on the type of laser and the technique used, but also on post-treatment care. The efficacy of Locobase Repair((R)) cream, which improves skin barrier function due to its content of natural skin analogue fats and cholesterol, was investigated.

METHODS

A total of 18 Caucasian patients underwent resurfacing for acne scars. Laser treatment was performed with a Sharplan 1020 CO(2) laser and a Silk Touch scanner. Locobase Repair cream (a water-in-oil cream with 63% lipids including natural components of stratum corneum: cholesterol, ceramide and free fatty acids) was applied daily to one side of the face and petrolatum was applied to the other. In addition, both sides were treated with a 2% fusidic acid cream.

RESULTS

There was a significant reduction of oozing during the first 2 days after CO(2) laser treatment on the sides treated with Locobase Repair cream (p < 0.05), CO(2) laser while from day 3 to day 7 no differences were demonstrated between the Locobase Repair cream and petrolatum. For the other parameters scored (scaling, oedema, erythema and pain), no significant differences between Locobase Repair cream and petrolatum were found. Furthermore, no significant differences were found between the two creams regarding the duration of wound healing and final cosmetic outcome. In all, 62% of the patients preferred to use Locobase Repair cream during the postoperative period, and 11% preferred petrolatum. The remaining 27% expressed no preferences.

CONCLUSION

The use of Locobase Repair cream as a post laser resurfacing treatment reduces tissue fluid oozing during the first 2 postoperative days, indicating a quick restoration of skin barrier and hence possibly a reduction in the incidence of wound infections as well as enhancing patient compliance due to less fluid oozing.

Effect of different moisturizers on SLS-irritated human skin

Moisturizers are widely used to treat irritant contact dermatitis (ICD). Their use is, however, not well-documented and standardized models for testing skin care products are needed to acquire documentation of their efficacy. The present study was undertaken to evaluate the effect of 6 commonly-used moisturizers on the recovery of irritated human skin. No commercial interests were involved in the study. 36 healthy volunteers had patch tests with SLS 0.5% applied on their forearms/upper arms for 24 h. After irritation of the skin, all volunteers had a moisturizer applied on one forearm/upper arm, respectively, 3 x daily for the following 5 days. The other forearm/upper arm served as an untreated control. Each moisturizer was tested on 12 volunteers and each volunteer tested 2 moisturizers at the same time. Evaluation was done on days 1, 3 and 8 by transepidermal water loss, electrical capacitance, laser Doppler flowmetry, DermaSpectrometry and clinical scoring. All 6 moisturizers were found to accelerate regeneration of the skin barrier function when compared to irritated non-treated skin. The most lipid-rich moisturizers improved barrier restoration more rapidly than the less lipid-rich moisturizers. We suggest this experimental model for further moisturizer efficacy testing.

Skin occlusion and irritant and allergic contact dermatitis: an overview

Occlusion, widely used to enhance percutaneous absorption of drugs, also increases penetration of other chemicals and antigens, and hence may exacerbate irritant and allergic contact dermatitis. This overview summarizes the adverse effects of occlusion.

The changes of epidermal calcium gradient and transitional cells after prolonged occlusion following tape stripping in the murine epidermis

Disruption of the epidermal permeability barrier causes an immediate loss of the calcium gradient, and barrier recovery is parallel with the restoration of the calcium gradient in the epidermis. Artificial restoration of the barrier function by occlusion with a water vapor-impermeable membrane abrogate the expected increase in lipid synthesis and retard the barrier recovery, as well as block the normalization of the epidermal calcium gradient. To clarify the long-term effects of occlusion after acute barrier perturbation, we studied the calcium distribution and epidermal keratinocytes response after occlusion with a water vapor-impermeable membrane immediately following tape stripping in the murine epidermis. Acute barrier disruption caused an immediate depletion of most calcium ions in the upper epidermis, obliterating the normal calcium gradient. When the skin barrier function was artificially corrected by occlusion, the return of calcium ions to the epidermis was blocked. After 2 h of air exposure or occlusion, the density of epidermal calcium precipitates remained negligible. The transitional cell layers appeared with occlusion, but not or negligibly with air exposure. By 6 h though, calcium precipitates could be seen, the density of the calcium precipitates with occlusion was more sparse than with air exposure. With the air exposure, the thickness of the stratum corneum had normalized and the calcium gradient nearly recovered to normal after 24 h. The longer the occlusion period, the greater was the increase of transitional cells. By 60 h of occlusion, the thickness of the stratum corneum had increased and the transitional cell layers had disappeared, in parallel with the calcium gradient which was almost normalized. These results show that prolonged occlusion of tape-stripped epidermis induced transitional cells and delayed the restoration of the epidermal calcium gradient, the stratum corneum was then restored, transitional cells having disappeared, in parallel with normalization of the epidermal calcium gradient.

Expression of epidermal keratins and the cornified envelope protein involucrin is influenced by permeability barrier disruption

In previous studies we have shown that experimental permeability barrier disruption leads to an increase in epidermal lipid and DNA synthesis. Here we investigate whether barrier disruption also influences keratins and cornified envelope proteins as major structural keratinocyte proteins. Cutaneous barrier disruption was achieved in hairless mouse skin by treatments with acetone +/- occlusion, sodium dodecyl sulfate, or tape-stripping. As a chronic model for barrier disruption, we used essential fatty acid deficient mice. Epidermal keratins were determined by one- and two-dimensional gel electrophoresis, immunoblots, and anti-keratin antibodies in biopsy samples. In addition, the expression of the cornified envelope proteins loricrin and involucrin after barrier disruption was determined by specific antibodies in human skin. Acute as well as chronic barrier disruption resulted in the induction of the expression of keratins K6, K16, and K17. Occlusion after acute disruption led to a slight reduction of keratin K6 and K16 expression. Expression of basal keratins K5 and K14 was reduced after both methods of barrier disruption. Suprabasal keratin K10 expression was increased after acute barrier disruption and K1 as well as K10 expression was increased after chronic barrier disruption. Loricrin expression in mouse and in human skin was unchanged after barrier disruption. In contrast, involucrin expression, which was restricted to the granular and upper spinous layers in normal human skin, showed an extension to the lower spinous layers 24 h after acetone treatment. In summary, our results document that acute or chronic barrier disruption leads to expression of keratins K6, K16, and K17 and to a premature expression of involucrin. We suggest that the coordinated regulation of lipid, DNA, keratin, and involucrin synthesis is critical for epidermal permeability barrier function.

The efficacy of different moisturizers on barrier recovery in hairless mice evaluated by non-invasive bioengineering methods. A model to select the potentially most effective product

Moisturizers (emollients) are used frequently on normal and diseased skin. However, only few studies have examined their effects in dynamic situations and in more clinically relevant settings. We evaluated the effect of 4 commonly used products in a hairless mice model after acute skin barrier perturbation with acetone. The efficacy was evaluated by measurement of the transepidermal water loss (TEWL) and electrical conductance at various time intervals during barrier repair. The test products were compared with acetone-treated air-exposed controls allowed to recover otherwise normally and with a known irritant product, chlorhexidine cream 1%. Locobase was the most effective product in correcting barrier function and significantly improved barrier function during early stages of barrier recovery (< 6 h) without interfering with late stages of barrier recovery (> 6 h). The irritant control product, chlorhexidine cream 1%, delayed barrier recovery in the late stages. The model makes it possible to evaluate the combined effects of exogenous and endogenous components on barrier repair and to select the potentially most effective products before performing more cumbersome and time-consuming field studies.