Overview of Drug Allergy: From Immunogenetic Basis to Practice

Drug therapy is often a balance between the beneficial and harmful effects of drugs. Drug allergic reactions are adverse reactions mediated by immunological mechanisms and usually not related to the pharmacological actions of the drug. They can be classified based either on the clinical presentation or the underlying immunological mechanism. Although uncommon, drug allergic reactions are unpredictable and can be very severe, even life threatening. The aim of this review was to provide clinicians from different medical specialties with a working tool to improve management of their patients with suspected drug allergy. It was conducted as a nonsystematic review, and attempts to describe the complexity of drug allergy. The information included ranges from pathophysiology to the heterogeneous clinical presentation, with a special focus on the drugs most frequently involved, as well as a classification of reactions and risk factors. Despite all advances in this challenging and complex field of allergy and clinical immunology, drug allergy is not yet fully established and understood. An exceptional contribution was brought by pharmacogenomics, even though a specific pharmacogenetic association has only been defined for a very limited number of drugs. Further studies are needed to obtain clearer answers when managing each individual case of drug allergy.