Skin tests with drugs help determine the cause and mechanism of drug hypersensitivity reactions. The diagnosis of adverse drug reactions is based primarily on history and clinical presentation. In type I, IgE-mediated allergic drug reactions, skin prick test and intradermal testing may provide rapid and supportive evidence for diagnosis or exclusion of IgE-mediated reactions. These tests often are more sensitive than laboratory assays for IgE antibodies to drug allergens, which are available only for a few drugs. Because intradermal skin tests occasionally induce adverse events, they should be performed by experienced personnel in an adequate environment.