Progressive evaluation of skin irritancy of cosmetics using human volunteers

Synopsis Cosmetics and toiletries should not elicit adverse reactions in use. Neither should they cause unacceptable effects if mis-used. Reliable prediction of these product attributes can be achieved by subjecting human volunteers to typical product exposure and to grossly exaggerated exposure. However, to ensure that volunteers do not sustain harmful effects there needs to be a cautiously progressive programme of testing. There must be adequate data on record to support exposure of human skin to the test material. The first contact with human skin should be in a small area, for short duration, and be very closely observed. When the effects are well within acceptable limits the exposure can be extended. As information accumulates, the application procedure can evolve towards simulation of the intended use of the product under controlled conditions, and eventual free use in consumer tests; and also towards exaggerated use to evaluate potential irritancy, using exaggerated frequency of use, exaggerated product concentration, or occlusive cover to promote skin penetration and enhance irritancy. Skin reactions under exaggerated exposure conditions do not necessarily mean that a product would be unacceptable under normal use conditions or when misused predictably. Therefore, appropriate standard products must be included in tests to provide relevant comparison when significant skin reaction does occur. Data will be presented to demonstrate progressive evaluation of irritancy of cosmetics and toiletries, based on expert assessment of visible skin reactions and on analysis of spontaneous and prompted comments about subjective effects, and including appropriate attention to the ethical requirements for tests involving human volunteers.