Drug reaction with eosinophilia and systemic symptoms (DRESS), also termed drug-induced hypersensitivity syndrome (DIHS), is a rare reaction to certain medications. It involves primarily a widespread skin rash, fever, swollen lymph nodes, and characteristic blood abnormalities such as an abnormally high level of eosinophils, low number of platelets, and increased number of atypical white blood cells (lymphocytes). However, DRESS is often complicated by potentially life-threatening inflammation of internal organs and the syndrome has about a 10% mortality rate. Treatment consists of stopping the offending medication and providing supportive care. Systemic corticosteroids are commonly used as well but no controlled clinical trials have assessed the efficacy of this treatment. DRESS is classified as one form of severe cutaneous adverse reactions (SCARs). In addition to DRESS, SCARs includes four other drug-induced skin reactions, the Stevens–Johnson syndrome (SJS); Toxic epidermal necrolysis (TEN), Stevens–Johnson/toxic epidermal necrolysis overlap syndrome (SJS/TEN); and Acute generalized exanthematous pustulosis (AGEP). The SCARs disorders have similar disease mechanisms. New strategies are in use or development to screen individuals at risk for DRESS to aid them in avoiding medications that increase the risk of DRESS. Alternative medications are used in all individuals testing positive for these predispositions. Prior to 1996, there were numerous reports on individuals presenting with a medication-induced disorder now recognized as the DRESS syndrome. For example, anticonvulsants in the 1930s, phenytoin in 1950, and other medications in the ensuing years were reported to do so. The reports often named the disorder based on the medication evoking it, e.g. the anticonvulsant hypersensitivity syndrome, allopurinol hypersensitivity syndrome, and dapsone hypersensitivity syndrome. In 1996, however, the term DRESS syndrome was coined in a report attempting to simplify the terminology and consolidate these various clearly related syndromes into a single underlying disorder. Signs and symptoms The symptoms of DRESS syndrome usually begin 2 to 6 weeks but uncommonly up to 8–16 weeks after exposure to an offending drug. Symptoms generally include fever, an often itchy rash which may be morbilliform or consist mainly of macules or plaques, facial edema (i.e. swelling, which is a hallmark of the disease), enlarged and sometimes painful lymph nodes, and other symptoms due to inflammation-based internal organ involvement, most commonly liver, less commonly kidney, lung, and heart, and rarely pancreas or other organs. Laboratory findings include increased blood eosinophil and atypical lymphocyte counts, elevated blood markers for systemic inflammation (e.g. erythrocyte sedimentation rate, C-reactive protein), and evidence