Estimations of incidence figures for drug allergy show a variation. In a French study of 2067 adults aged from 20 to 67 visiting a health-care center for check-up examination, 14.7% of the study group reported reliable histories of systemic drug reactions.
Others have stated that allergic drug reactions account for 5-10% of adverse drug reactions. In a Swiss drug monitoring program, about 17% of hospitalized patients showed adverse drug reactions, 5.4 -5.9% appeared to be allergic.
Numerous mechanisms have been implicated, but several remain obscure and this lack of knowledge accounts for the difficulties in differentiating allergy from other side effects, assessing the incidence, risk factors, and management strategy for diagnosis and prevention.
This book was written as a practical guide to allergy diagnosis management and the main drugs responsible. We have tried to specify the main clinical manifestations and risk factors for each of them, as well as the diagnostic methods (in vivo and, where possible, in vitro), known mechanisms and management.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.