Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome is an adverse drug reaction caused by an apparent group of drugs which can cause 10-20% mortality. It is characterized by a latency period ranging from 3 weeks to 3 months after the introduction of the offending drug. The syndrome is defined by the presence of fever, rash, eosinophilia, atypical lymphocytes and multiorgan involvement. We present a 39-year-old woman who developed fever, nausea, a pruritic erythematous maculopapular rash and facial edema during her sixth week of the treatment with allopurinol as a case of DRESS syndrome. Diagnosis was confirmed by the drug rash, eosinophilia and systemic involvement including adenopathy, toxic hepatitis and pericardial effusion. Allopurinol was discontinued and intravenous prednisolone 60 mg/day was started. The patient’s clinical appearance and eosinophilia improved within first 2 days. Awareness of hematologic abnormalities and systemic involvement along with drug rush, by physicians is critical for early diagnosis of this life-threatening syndrome. J Med Cases. 2014;5(7):420-422 doi: https://doi.org/10.14740/jmc1811w