According to most studies, allergic reactions represent 35%-50% of all untoward reactions to drugs, yet the pharmacological literature concerning the clinical aspects, diagnosis, and pathophysiological mechanisms of drug allergy is markedly less extensive than reports dealing with the toxicological or pharmacological effects of drugs. The main reasons for this state of affairs may be on the one hand that until a few years ago the pathophysiological mechanisms of the various types of allergic reactions were not well understood, and on the other hand that objective diagnosis of a drug allergy...