Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe drug-induced reaction. It is characterized by fever, skin eruption, lymphadenopathy, haematological abnormalities and involvement of internal organs. We describe the case of a 74-year-old woman, who developed DRESS, due to intake of allopurinol. She was admitted to the hospital 6 weeks after she had begun taking allopurinol with fever, maculopapular erythema, lymphadenopathy and general malaise. Blood tests revealed eosinophilia, lymphocytosis, severe inflammation and involvement of liver and kidney. PET-CT showed increased FDG uptake in several lymphnotes. She was diagnosed with DRESS, the culprit drug was withdrawn and she was given oral prednisolone. Symptoms resolved within a month. DRESS is a serious condition with mortality up to 10%. It is associated with diagnostic difficulties, as the clinical symptoms are variable and may mimic other conditions. Our case focuses on the recognition and treatment of DRESS.