THE INVITRO SKIN CORROSIVITY TEST - DEVELOPMENT OF METHOD USING HUMANSKIN

To meet the EEC regulations for classification, packaging, labelling a nd transportation, many new substances have to be tested for their pot ential cutaneous toxicity. At present, this is assessed in an in vivo rabbit dermal test. The in vitro skin corrosivity test has been develo ped to identify those substances which would cause a corrosive respons e in an in vivo test, thereby alleviating the need to assess corrosive substances in an in vivo test. The method, which uses ex vivo rat ski n, is based on the observation that corrosive substances cause a signi ficant reduction in the electrical resistance of skin. The present stu dy investigated the possibility of using human skin in the in vitro sk in corrosivity test to provide a means of direct assessment of effect in humans. 12 substances were assessed in this model. The transcutaneo us electrical resistance (TER) following treatment with distilled wate r is essentially the same as that for untreated skin. Of the six prepa rations that would be formally classified as corrosive by the EEC, on the basis of a 4-hr rabbit covered patch test, all caused a sharp fall in the TER for each specimen of human skin on which they were tested. On the basis of these data, the TER threshold for determination of po tential corrosivity was judged to be 11.0 kohms/disc of skin. For the five preparations which would be classified as irritant or would not r equire a label, the reduction was usually much less marked. Continuing work in this laboratory is directed towards an assessment of a much w ider range of chemicals using the human skin in vitro model, ultimatel y with a view to its use as a method of detecting those substances whi ch may be corrosive to the skin of humans, leading to their classifica tion and appropriate labelling.