The in vitro skin corrosivity test. Comparison of in vitro human skin with in vivo data.

Regulations require that many substances and chemicals are tested for their cutaneous toxicity potential. At present this is assessed in an in vivo rabbit dermal test. A rapid, robust and reliable alternative for testing the corrosive potential of substances is the in vitro skin corrosivity test, which alleviates the need to assess corrosive substances in an in vivo test. The method is based on the observation that corrosive substances cause a significant reduction in the electrical resistance of skin. It was anticipated that the more resistant nature of human skin would lead to a number of substances being classified as non-corrosive, contrary to historical in vivo animal data. In the present study 15 surfactants and eight fatty acid substances were tested on human skin in the assay. Three surfactants and four fatty acids were classified as corrosive in vivo. In the assay, the three surfactants were identified as corrosive, but all the fatty acid substances were found to be non-corrosive. It is suggested that the fatty acid substances labelled as corrosive on the basis of animal data are over-labelled, that is, in humans the substances would not lead to a corrosive effect. It is envisaged that the in vitro human skin corrosivity test will be used in conjunction with human patch tests, currently being developed. This approach should allow a reduction in animal testing and a more relevant classification of skin irritation potential to humans.