[Identifying and understanding drug allergies].

Drug hypersensitivity reactions frequently occur in hospitalized and out-patients. Clinical presentations are numerous and heterogeneous, from a mild urticaria to a dramatic anaphylactic shock and an extensive bullous skin disease. Allergic reactions are unpredictable reactions, related to immunologic mechanisms. Some reactions mimic allergic reactions but no drug specific antibody or T cell proliferation can be demonstrated. A true diagnosis is rarely set up and the tools for it are lacking. In this review, we will focus on the available epidemiological data concerning these reactions, including data on incidence and mortality and on the most recent advances in the pathophysiology and allergy diagnosis of drug hypersensitivity reactions.