Aim of the study: There is a widely accepted need for systemic investigations regarding the efficacy of skin protection products used in occupational health care. The efficacy of such products has been established for water-soluble irritants, such as SLS, but the use in studies of lipid-soluble irritants, such as toluene, poses experimental and ethical problems. The aim of the invitro study using toluene was to demonstrate the skin protecting properties of eight commercially available products and two positive controls (lanolin alcohol, petrolatum) and one market product (W/O emulsion) used as negative control. Four of the eight products were emulsions of the O/W type, three products were suspensions and one product was described as a hydrogel formulation. All of them claimed to be protective either against waterinsoluble or water-soluble/water-insoluble irritants. Method: The viable, natural skin of the isolated, perfused, bovine udder (BUS model) was used as the in-vitro model. Continuously oxygenised perfusion maintains skin metabolism and the performance of the barrier within the horny layer for more than 8 hours. Using whole skin biopsies the degree of irritation is measured by evaluating the irritancy (PGE2 concentration) and cytotoxicity (MTT assay). The BUS study design allows the simultaneous evaluation of the status of the untreated skin, the skin-compatibility of the products/reference substances, the irritation capability of toluene itself, and finally the irritation capability of toluene applied to the skin pre-treated with the products 15 minutes previously. The first samples of whole skin biopsies were taken 15 minutes after the toluene was applied. The following exposure periods were 1 hour and a prolonged exposure period of 5 hours. In addition to the main study using the hairy skin (follicular) of the lateral udder (n = 4) in a 2nd study (n = 2) the hairless skin of the teats was used for the assay. Results: The local effects of toluene are based on progressive cytotoxicity and a slight increase in the PGE2 concentration in the skin tissue. Both reference substances (lanolin alcohol, petrolatum) reduced significantly the toluene-related alterations by approx. 70 % within 15 minutes after application of the toluene. In contrast, the negative reference (W/O emulsion) did not influence the tissue reactions induced by toluene at all. Two (suspension, O/W emulsion) of the eight market products were comparable to the reference substances regarding their protective potential. Three market products (suspension, O/W emulsion) had a moderate degree of protective potential, while three other market products (suspension, O/W emulsion, and hydrogel) had a low degree of protective potential. After exposure for 1 hour and 5 hours, only the negative control and the products with the low performance demonstrated a distinct increase in protective potential. No distinct difference was observed between the results after exposure for 1 hour and 5 hours. Similar results were obtained after application on the hairless skin of the teats. Conclusions: None of the eight market products was comparable with the negative reference (market product) formulated as a W/O emulsion. This product claimed to protect against water-soluble irritants only. In this assay it proved to be ineffective against lipidsoluble irritants, such as toluene. All skin protection products tested in the BUS model showed a certain degree of protective potential against the lipophilic model toxicant, toluene.
