Losio, N., Bertasi, B., D’Abrosca, F., Ferrari, M., Avalle, N., and M. Fischbach. In Vitro Product Safety Evaluation: A Screening Study on a Series of Finished Cosmetic Products. ATLA. 1999. 27: 351.

The present study was designed to explore the possibilities for evaluating the cutaneous toxicity of complex cosmetic formulations by using representative model cell culture systems. Primary human dermal fibroblast, and epidermal keratinocyte, cultures were individually exposed to a selection of finished cosmetic products with known in vivo irritancy levels for 24 hours. Corresponding in vitro skin irritating potentials were assessed by performing both the neutral red uptake assay and the MTT reduction assay. The test series comprised 22 finished cosmetic products, including skin-care creams and gels, lotions, cleansing formulations, lipsticks, eye-liners, mascaras, face powders and foundations. The test products were suspended in either water or dimethylsulphoxide (DMSO), where appropriate, and tested against solvent control preparations. For most of the products, NRU50 and MTT50 values could be established using a standard test concentration range of 0.1-10 ug/ml. According to these results, the products were classified as potentially irritant or non-irritant. In most cases, the NRU50 had no effect on the overall classification of the products. Both cell types performed equally well in terms of specificity, sensitivity and concordance when compared to known in vivo data from human patch test results. To summarise, the results from this preliminary data set are encouraging and confirm that human primary keratinocytes and fibroblasts can be usefully employed as a prescreening filter of candidate cosmetic formulations, thus significantly reducing further animal or human volunteer experimentation.