Résumé

• Defined as a drug reaction that affects the structure or function of the skin, its appendages, or mucous membranes.
• Common adverse skin reactions to systemic drugs include: maculopapular rashes; urticaria and angio-oedema; the spectrum of rashes encompassing erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis; and fixed drug eruptions. Together these account for about 95% of all drug-induced eruptions.
• Any drug can cause an allergic reaction; those commonly implicated include beta-lactam antibiotics, muscle relaxants used in anaesthesia, sulphonamides and structurally related drugs, contrast media, and gelatins.
• A history of previous allergic reactions to drugs should always be taken before prescribing.
• Skin tests (prick tests, intradermal tests, patch tests) can occasionally be useful in diagnosing allergic reactions retrospectively, especially contact dermatitis.
• After anaphylactic reactions, serum tryptase activity can help in diagnosis.