Acute irritation tests in risk assessment.
The two most important elements in assessing the risk of topical injury from a chemical are its biological properties, in the context of skin and mucous membrane damage, and the likelihood and likely nature of topical contact with the chemical. Appropriate biological tests in model systems should be based on the probable circumstances of exposure. Topical contact takes place under two distinct sets of circumstances--intentional and accidental. Chemicals that are intended to come into contact with skin and mucous membranes include cosmetics and dermatological preparations. For such compounds the frequency and extent of skin contact is predictable and any irritant effects are unacceptable. The absence of irritant effects is established by testing in human volunteers or experimental animals. Since animal skin and mucous membranes are more susceptible to irritants than those of man, the amounts or concentrations tested need not be greater than those intended for human use. It is hoped that validated alternatives to animal models will soon be available. For household or industrial chemicals where skin and/or mucous-membrane contact occurs accidentally, topical contact should generally be avoided. In such cases the objective of irritancy testing should be to establish which compounds are particularly irritant and therefore need extra care in handling. We are convinced that this latter objective can be achieved by simpler and less cruel tests than the Draize eye-irritation test.