To gain a better understanding of the interaction of the model detergent sodium lauryl sulfate (SLS) with the stratum corneum, we investigated systematically the ultrastructural changes of the epidermal barrier and the nucleated parts of the epidermis after the occluded application of different concentrations of SLS in human. Different application models were investigated. Two of the three irritation procedures (long duration exposure and the repetitive exposure for 3 d) provoked damage of the nucleated parts of the epidermis and alterations of the lower parts of the stratum corneum. Here, the extrusion and transformation of lamellar body derived lipids into lamellar lipid bilayers were disturbed; however, the upper portions of stratum corneum displayed intact intercellular lipid layers that contradict the long-standing belief that surfactants damage the skin by delipidization. Furthermore, we investigated ultrastructurally and by measurement of transepidermal water loss the influence and protective capacity of a lipophilic barrier cream on acute irritant contact dermatitis. The irritant contact dermatitis was induced by the standardized cumulative short application model with two SLS concentrations (0.5% and 0.75%). The cumulative type of exposure simulates daily living more realistically. Because most of the previous tests have been performed on the human forearm or back, we analyzed whether the pattern of response was similar on both sites. The back showed a higher level of irritant reaction, but the pattern of irritant response proved to be similar to the forearm. Application of the barrier cream before and during irritation showed a decrease of transepidermal water loss enhancement with 0.5% SLS by 58% (back) and 49% (arm) and after irritation with 0.75% SLS by 56% (back) and 43% (arm). Because the experimental result correlated with the clinical experience, the development of the cumulative short exposure model might help to predict and to discriminate the efficacy of barrier creams.

Although skin protective products to prevent irritant skin reactions are in wide use, neither standardized test models to prove differences in efficacy exist, nor has the quality or the reproducibility of results been evaluated in a multicentre approach. This should be mandatory when developing or testing skin care products. Therefore, we have designed a multicentre study in an approach to find a standardized test procedure for the evaluation of skin protective products. In this irritation study, a repeated short-time occlusive irritation test (ROIT) with a standardized protocol has been evaluated in 2 phases (12 days and 5 days protocol) in 4 (n=20) respectively 6 (n=33) skilled centres. The skin reaction was induced by 2 irritants (0.5% aq. SLS and toluene, 2x a day for 30 min). Its modification by 3 different cream bases with different hydrophilicity was analyzed. The irritation was monitored by bioengineering methods (TEWL measurement, colorimetry) and by clinical scoring. The evaluation showed that significant results could already be achieved with the 5-day protocol. Furthermore, in spite of the expected inter-centre variations due to heterogeneity of the individual threshold of irritation, interpretation of clinical score, and inter-instrumental variability, the ranking of the vehicles regarding reduction of the irritant reaction was consistent in all centres.

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Aqueous extracts of polysaccharide-containing plants are widely used in therapy for irritated mucus membranes in the pharynx region. In order to prove the existence of mucilaginous effects of polysaccharide hydrocolloids on epithelia an ex vivo system based on porcine buccal membranes was established. The tissue culture was stable and there was no indication of cytolytic processes during the 5 hour incubation period. This was confirmed through histological studies and the respective LDH values as toxicity marker. The test system was shown to discriminate the adhesive effects of different raw polysaccharides, obtained from a variety of medicinal plants. While polysaccharides from Altheae officinalis, Plantago lanceolata, Malva moschata, or Tilia cordata showed only moderate bioadhesion to epithelial tissue, strong adhesive processes were observed with polysaccharides from Fucus vesiculosus and Calendula officinalis. The adhesive effects were concentration-dependent. Histological studies of membranes, incubated with a fluorescence-labelled rhamnogalacturonan, indicated the presence of distinct polysaccharide layers on the apical membrane surface. With these results, adsorption effects of certain polysaccharides on mucus membranes were shown for the first time. Such effects suggest that this may account, at least in part, for the therapeutic effects of mucilage-containing plants in the treatment of irritated buccal membranes.