Allergy testing in serious cutaneous drug reactions--harmful or beneficial?

We report on 3 cases of adverse cutaneous drug reactions of erythema multiforme type. Despite the serious previous clinical conditions, patch tests with the possible causative drugs have been performed in all our patients, because of multiple candidate drugs and the need of the patients for further treatment with at least some of the agents. We demonstrate that patch tests are a good and safe approach to initial evaluation of the nature of a cutaneous drug reaction. In the case of a positive patch test reaction to one of the substances, re-exposure to the non-reactants in a clinical setting is recommended. If a one-side-blinded placebo-controlled challenge test is well tolerated, then the clinician should be able to reintroduce drugs previously suspected as causing the allergy.