Introduction: Classification, Terminology, Epidemiology, and Etiology of Cutaneous Adverse Drug Reactions

Whenever a cutaneous adverse drug reactions (cADR) is suspected, it is important to establish the dermatological diagnosis, since reaction patterns may differ in causality, time latency between the beginning of drug use and reaction onset, and prognosis. Few epidemiologic studies have been performed on frequent non-life-threatening cADR, such as maculopapular exanthema, fixed drug eruption, and urticaria. For rare but life-threatening severe cutaneous adverse reactions, e.g., Stevens-Johnson syndrome/toxic epidermal necrolysis, acute generalized exanthematous pustulosis, and drug reaction with eosinophilia and systemic symptoms, several epidemiologic studies have been or are currently performed. They allow for estimation of incidence rates, demographic data, and drug risks.