Patch testing for allergic contact dermatitis in the allergist office.

The identification of allergens responsible for allergic contact dermatitis (ACD) is key to the management of this disease. The patch test (PT) is the only safe, objective, scientific, and practical method for the diagnosis of ACD. There is no single PT panel that will screen all the relevant allergens in a patient's environment. It is generally thought that 20 to 30 allergens in routine screening tests can identify 50% to 70% of clinically relevant ACD. However, the usefulness of patch testing is enhanced with the number of allergens tested. Although the PT might be simple to apply, it might be difficult to read, interpret, and correlate to the patient's symptoms. A familiarity with the patient's environment, the process of the industry in that environment, and the uses of various chemicals in the industry is needed in most cases.