Immune reactions to drugs and diagnostic agents.

Adverse reactions to drugs are common, but only a small percentage of these reactions results from a specific immune reaction to a drug. Over-reactivity of almost any part of the immune system can result in an immunologically mediated drug reaction; however, T cell-and immunoglobulin E-mediated reactions are the most common. The reactions are unpredictable and can involve any part of the body, although skin is most frequent. The various pathogenic mechanisms are discussed, along with diagnostic testing, factors predisposing to drug allergy, and reactions to individual drugs and therapeutic reagents.