ALLERGIC AND IMMUNOLOGICAL SKIN DISORDERS

The skin represents a unique immunologic organ poised to protect the h ost from invading organisms and environmental antigens. The skin is al so an important target for a variety of allergic and autoimmune respon ses. Mast cells are key to the pathogenesis of urticaria, angioedema, and mastocytosis. Atopic dermatitis is the consequence of an immunoreg ulatory abnormality resulting in a skin-directed T helper type 2 respo nse. Allergic contact dermatitis is an example of classic delayed type hypersensitivity. Circulating autoantibodies against the epidermis ar e a key mechanism by which bullous skin diseases occur.