[Drug allergies: a public health problem].

Adverse drug reactions occur in 10 to 20% of hospitalized patients and up to one third are due to allergic and pseudoallergic reactions. Allergic reactions are unpredictable reactions related to immunologic mechanisms. Pseudo-allergic reactions mimic allergic reactions but no drug specific antibody or T cell proliferation can be demonstrated. A true diagnosis is rarely set up and the tools for it are lacking. In this review, we will focus on some epidemiological data concerning these reactions, including data on incidence, mortality and cost.