Patch testing to cosmetics and topical drugs.

Evaluating patients with a possible cosmetic or medicament allergy is an excellent way for dermatologists to become acquainted with using patch test substances beyond the standard tray. Testing should include standard tray allergens and almost all topical products themselves. False-positive and false-negative results must always be considered in evaluating patch test results. Repeat open application testing can be useful in confirming patch test results, but it is best to test each ingredient separately. If they are willing to take the time, dermatologists can easily and efficiently evaluate these patients.