In Vivo Irritation

Abstract

Skin irritation is a localized nonimmunologically mediated inflammatory process. It maymanifest 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 (Table 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 are more 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.