BACKGROUND Allopurinol is the first-line therapy for the treatment of symptomatic hyperuricemia (gout). In clinical practice, there is a tendency to overmedicate asymptomatic patients who have elevated serum urate. Because of this practice, serious and life-threatening reactions such as Stevens-Johnson syndrome (SJS) or the more dramatic toxic epidermal necrolysis (TEN), both frequently caused by uricostatics, may occur. To increase awareness of these complications, we present a case with fulminant TEN caused by allopurinol. CASE REPORT A 75-year-old woman noticed a mildly itching skin rash accompanied by fever, shivering, and weakness approximately 3 weeks after taking newly prescribed allopurinol. The initial clinical examination revealed a generalized maculopapular exanthema. An adverse drug reaction was recognized, and allopurinol was discontinued. Ambulatory supportive therapy using prednisolone and cetirizine was started but failed. The patient developed a progressive exanthema with painful widespread blistering, skin peeling, and mucosal and conjunctival lesions. After recurrent presentations to the Emergency Department, the patient was transferred to our Intensive Care Unit (ICU). The clinical picture confirmed the suspected diagnosis of TEN. Massive fluid replacement, prednisolone, and cyclosporine were used as anti-inflammatory therapy. Polyhexanide and octenidine were applied for local treatment. All treatment measures were guided daily by a multidisciplinary team. After 7 days in the ICU, the patient was transferred to the Dermatology Department and was discharged from the hospital 42 days later. CONCLUSIONS With the prescription of allopurinol, there should be awareness of potentially life-threatening complications such as SJS or TEN. Patients with SJS or TEN should be immediately transferred to an ICU with dermatological expertise and multidisciplinary therapy.