ABSTRACT
Serious adverse reactions to cosmetic ingredients and preparations are actually infrequent. However, side effects do occur and are by no means rare. The unwanted effects of cosmetics can be classified into the following different categories (1-4):
1. Irritation and contact urticaria 2. Contact allergy 3. Photosensitive reaction (photoallergy and photoirritation) 4. Acnegenesis and comedogenesis 5. Color changes of the skin and appendages 6. Systemic side effects 7. Other local side effects
When considering skin-irritation symptoms, we are dealing with nonimmunological mediated inflammation of the skin induced by external agents. Chemicals irritants are the major cause, but mechanical, thermal, climatic, and UV and IR light are also important factors or cofactors of irritancy (5). This nonimmunological skin irritancy reaction comprises two forms: the acute irritant reaction with a monofactorial cause (detergent, acid, oxidant, etc.) and the chronic multifactorial form. The symptoms of skin-irritation are well known: erythema, dryness, scaling, itching, burning, and tingling. These clinical symptoms are described by some authors as objective irritation (1-4). Because these symptoms are clearly perceptible, in vivo testing in humans can easily and reliably detect strong and moderate irritant ingredients and eliminate these potential hazards. However most cosmetic-use ingredients do not produce acute irritation from a single exposure because they are mild or very mild and consequently difficult to detect. Nevertheless, they may produce inflammation after repeated application on the same area of the skin, which is referred to as cumulative irritation.
