Contact Dermatitis
Contact dermatitis is eczema caused by an external contactant: irritant disease is dose-dependent barrier injury, whereas allergic disease is a delayed T-cell-mediated reaction in a sensitised person.
Definition
Contact dermatitis is inflammation of the skin caused by contact with an external agent. Irritant contact dermatitis results from direct non-immunological injury to the skin barrier; allergic contact dermatitis is a delayed, cell-mediated hypersensitivity reaction in a sensitised person.
First principles
Irritant disease is barrier failure
Irritant contact dermatitis is direct chemical, physical or mechanical injury to the skin barrier. Repeated water exposure, wet work, soaps, detergents, solvents and other irritants can overwhelm barrier repair; no prior sensitisation is required, and the risk rises with concentration, frequency and duration of exposure. It commonly causes occupational hand dermatitis.
This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.