Diagnostic Patch Testing

Abstract

Patch testing is a well-established method of diagnosing contact allergy and allergic contact dermatitis, a delayed type of hypersensitivity (type-IV reaction). Patients with a history and clinical picture of contact dermatitis are exposed to the suspected allergens, materials or products under controlled conditions to verify the diagnosis. Besides testing patients with hand, arm, face or leg eczema, testing of other types of eczema (atopic, seborrhoic dermatitis, nummular eczema) is sometimes indicated, especially when the dermatologist suspects contact allergy to prescribed topical medicaments and their vehicles. The procedure can also be used before recommending alternative protective gloves, skin care products, corticosteroids, etc. to a particular patient. If the patient does not react to the alternatives tested, it is very unlikely that the same individual will react to the products in ordinary use.