drug allergy,hypersensitivity reaction totherapeutic agents that occasionally occurs on subsequent exposure to adrug against which an individual has already producedantibodies. Various drugs are linked to allergic reactions; examples includetetracyclines,digitalis,ibuprofen,aspirin,penicillin, and drugs used to treatautoimmune disease.

Symptoms of drug allergy vary with the drug and the sensitivity of the affected person but include, as separate reactions, skin rash,hives (urticaria), wheezing, serum sickness, and, rarely,anaphylaxis (collapse of thecirculatory system with accompanying respiratory symptoms). Several drugs can successfully counteract these allergic symptoms; after drug allergy has been established, lifelong avoidance of the offending drug, and often of its derivatives, must be observed.