ABSTRACT
Irritant Dermatitis Skin irritation is a localized nonimmunologically mediated inflammatory process. It may manifest objectively with skin changes such as erythema, edema, and vesiculation or subjectively with the complaints of burning, stinging, or itching, with no detectable, visible, or microscopic changes. Several forms of objective irritation exist (Tabel 1). Acute irritant dermatitis may follow a single, usually accidental, exposure to a potent irritant and generally heals soon after exposure. An irritant reaction may be seen in individuals such as hairdressers and wet-work-performing employees,who aremore extensively and regularly exposed to irritants. Repeated irritant reactions may develop into a contact dermatitis, which generally has a good prognosis. Other forms of irritant dermatitis include delayed acute irritant contact dermatitis, which occurs when there is a delay between exposure and inflammation, and cumulative irritant dermatitis, which is the most common form of irritant contact dermatitis. After exposure, an acute irritant dermatitis is not seen, but invisible skin changes occur, which eventually lead to an irritant dermatitis when exposure reaches a threshold point. This may follow days, weeks, or years of exposure (1). These various forms require specialized models to predict their occurrence after exposure to specific products.
Need for Models Prevention of skin irritation is important for both the consumer who will suffer from it and for the industry, which needs a licensable and marketable product. Accurate prediction of the irritation potential of industrial, pharmaceutical, and cosmetic materials is therefore necessary for the consumer health and safety and for product development. Presently, animal models fulfill licensing criteria for regulatory bodies. In the European Union (EU), animal testing for cosmetics was to be banned in 1998; however, the deadline was extended to June 30, 2000, because scientifically validated models were not available. Until alternative models can be substituted, in vivo models provide a means by which a cosmetic can be tested on living skin, at various sites, and under conditions that should closely mimic the intended human use.
