The patient was a 51-year-old man who had been prescribed carbamazepine for right third-branch trigeminal neuralgia. He had stopped taking the medication after the neuralgia resolved. When the neuralgia recurred, he resumed medication, and about 1 month later he developed fever, fatigue, cervical lymphadenopathy, generalized skin flushing, facial edema and perioral vesicles, and was admitted to Ichikawa General Hospital, Tokyo Dental College. Oral findings showed reddening and erosion of the buccal mucosa. Routine laboratory examination revealed leukocytosis and hepatic dysfunction. Human herpesvirus 6 antibody titer remarkably increased during development of eruptions. These findings led to a diagnosis of drug-induced hypersensitivity syndrome. Carbamazepine was discontinued, and prednisolone (30 mg/day) was started and tapered based on improvement of symptoms. Because skin symptoms recurred after he was discharged 15 days after admission, the dose of prednisolone was increased and the symptoms finally disappeared. The patient has experienced no further recurrence.