THE DEVELOPMENT AND EVALUATION OF IN-VITRO TESTS FOR PHOTOIRRITANCY

Photoirritancy, a reversible inflammatory reaction of the skin after c hemical contact and UV radiation exposure, is increasingly observed as a side-effect of both cosmetics and certain systemic drugs. Despite t he quantity of in vitro data available, none of the current animal mod els can be viewed as fully predictive of human exposure. It is therefo re considered that the emphasis of future work should be the developme nt and evaluation of in vitro assays. The aim of this study was to est ablish the interlaboratory performance of a physicochemical method, SO LATEX-PI. 12 pure chemicals at several concentrations were evaluated i n the presence of UVA. In addition, a lymphoid cell assay was undertak en to allow a direct in vitro/in vitro comparison. The overall correla tion between the laboratories was good when expressed in terms of a po sitive or negative result. However, there were some interlaboratory di screpancies, which were compounded by the lack of unequivocal in vivo data. Despite these discrepancies, both laboratories did agree on the final classification of nine of the 12 chemicals in the SOLATEX-PI sys tem, based on the highest concentrations tested. The cellular photoirr itancy assay, in contrast, predicted the correct classification for on ly eight of the 12 chemicals tested compared with the in vivo data sup plied by IVI.