[Drug allergies].

Drug allergies can be classified into three subgroups which differ in their pathophysiology and require different diagnostic steps: 1. classical drug allergies, which are directed against the drug itself, a reactive metabolite or some contaminant of the drug, 2. pseudoallergic reactions, which are caused by non-immune mediated degranulation of mast cells and basophils, and 3. autoimmune reactions, in which the drug elicits an immune reaction to autologous structures. A very detailed accurate history is of the greatest importance in the clarification of a suspected drug allergic reaction, as well as experience with the drug. In addition, skin tests, serological tests and the lymphocyte transformation test may be useful. One should differentiate between tests which imitate the drug-elicited allergic reaction (i.e., Coombs test in drug-induced hemolytic anemia) and tests which solely indicate a sensitization and the tests must be interpreted accordingly.