Multicentre study for the development of an in vivo model to evaluate the influence of topical formulations on irritation

Although skin protective products to prevent irritant skin reactions are in wide use, neither standardized test models to prove differences in efficac y exist, nor has the quality or the reproducibility of results been evaluat ed in a multicentre approach. This should be mandatory when developing or t esting 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 o cclusive irritation test (ROIT) with a standardized protocol has been evalu ated 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% a q. SLS and toluene, 2x a day for 30 min). Its modification by 3 different c ream bases with different hydrophilicity was analyzed. The irritation was m onitored by bioengineering methods (TEWL measurement, colorimetry) and by c linical scoring. The evaluation showed that significant results could alrea dy be achieved with the 5-day protocol. Furthermore, in spite of the expect ed inter-centre variations due to heterogeneity of the individual threshold of irritation, interpretation of clinical score, and inter-instrumental va riability, the ranking of the vehicles regarding reduction of the irritant reaction was consistent in all centres.