How does allergic contact dermatitis occur?
Allergic contact dermatitis is a cell-mediated, type IV, delayed hypersensitivity reaction that results when specific antigens enter under the skin. This means that the offending substance to which you are allergic combines with a special receptor and travels to the second layer of skin, the dermis, where the immune cells (T cells) become sensitized. The next time that you are exposed to the antigen, the allergic reaction takes place. What are the common causes of allergic contact dermatitis? The most common offenders in allergic contact dermatitis are plants of the Toxicodendron genus (e.g., poison ivy, poison oak, poison sumac). Other substances include nickel sulfate (various metal alloys), potassium dichromate (cements, household cleaners), formaldehyde, ethylenediamine (dyes, medications), mercaptobenzothiazole (rubbers), thiuram (fungicides), and paraphenylenediamine (dyes, photographic chemicals). Irritant contact dermatitis occurs when an irritant produces direct local toxic ef
