Drug allergies are adverse reactions resulting from immunologic responses to drugs or their metabolites. These reactions result in predictable patterns of organ-specific or systemic hypersensitivity that usually recur on subsequent exposure to the same drug. Although diagnostic testing for drug allergy is available for only a few drugs, protocols have been developed to assist in management of allergic reactions to many drugs and biologic agents. Other protocols assist in the management of patients who develop drug reactions while undergoing multiple drug therapy or those with a history of adverse drug reactions who again require treatment for the same condition.