Contact dermatitis

Abstract

Contact dermatitis occurs at the site of contact with irritating or antigenic substances and can be divided into irritant and allergic types. Allergic contact dermatitis is a type IV T - cell-mediated reaction occurring in a sensitized individual after contact with the antigen/allergen. In allergic contact dermatitis, a skin-applied antigen is taken up by epidermal Langerhans cells and transported with the afferent lymph to the regional lymph nodes. Here, naive T lymphocytes are sensitized to become antigen-specific effector T cells, which then leave the lymph node and enter the circulation, and are requrited to the skin by means of specific cell surface molecules to form the infiltrates. Irritant contact dermatitis is the result of non-immunologic damage to the skin by an irritant, i.e. a chemical or physical agent that produces cell damage if applied for a sufficiently long period in a sufficiently high concentration.