[Epicutaneous testing (patch testing)].

At present, patch testing is the only practical way of diagnosing allergic contact dermatitis, manifested as delayed hypersensitivity (type IV reaction). It can serve to confirm relevant allergens, but may also help to exclude suspected contact sensitivity. The test procedure varies somewhat from one clinic to another but has been standardized by the International Contact Dermatitis Research Group. Choice of test materials and their application may appear simple, but test readings and interpretation of results are most important. Positive reactions can be positive (allergic) or false positive (irritant), and relevant or not relevant to an existing or previous dermatitis. The dermatologist is the person best qualified to diagnose contact dermatitis by this test procedure.