The phenomena of idiosyncrasy to drugs have long presented a problem to physicians, but it is only recently that progress has been made in elucidation of the mechanism of many of these reactions. A considerable number of reactions are due to immunologic hypersensitivity or allergy, unrelated to the drug action. The recognition of allergic manifestations as such is made more difficult by the pharmacologic activity of these agents, and in some cases the distinction between allergic and toxic reactions cannot be made with certainty.
In recent years, numerous studies of the histologic lesions of drug hypersensitivity, as distinguished from toxic effects, have been reported. Arteritis, with localized fibrinoid and hyaline degeneration of the media and perivascular infiltration, has been described in allergy to a number of different drugs.1 Focal necrosis of the myocardium, liver, spleen and other organs, with infiltration of mononuclear cells, is also characteristic. The