The role of patch testing for chemical and protein allergens in atopic dermatitis.

Many patients who present for evaluation of allergic contact dermatitis have an atopic diathesis. Although the immunologic basis of atopic dermatitis differs from that of allergic contact dermatitis--and patients with atopic dermatitis are less easily sensitized under experimental conditions--atopic patients do develop allergic contact dermatitis, and patch testing is a valuable part of their medical care. Delayed (7-day) patch test readings are especially important in atopic patients to distinguish allergy from irritancy and to evaluate for steroid allergy. The utility of atopy patch tests to aeroallergens such as dust mite is increasingly recognized; aeroallergens may be the cause of a type of protein contact dermatitis.