The DRESS syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms) is a severe immunological drug reaction. It differs from other drug reactions in that it: a) is caused by a particular set of drugs; b) typically occurs after a delay of 2 to 8 weeks following intake of an offending drug; c) presents with a specific set of signs and symptoms (i.e. modest or extreme elevations in blood eosinophil and atypical lymphocyte counts; acute onset of a skin rash; lymphadenopathy; fever; neuralgia; and involvement of at least one internal organ such as the liver, lung, or heart; d) develops in individuals with particular genetic predispositions; and e) involves reactivation of latent viruses, most commonly human herpesvirus 6 or more rarely human herpes virus 5 (i.e. human cytomegalovirus), human herpesvirus 7, and human herpesvirus 4 (i.e. Epstein–Barr virus). These viruses usually become dormant after infecting humans but under special circumstances, such as drug intake, are reactivated and may contribute to serious diseases such as the DRESS syndrome.
