Skin eruption with mild itching of the hands and feet developed in a man in his 90s 1 month after he was hospitalized following a traffic accident. Scabies was diagnosed in an attending nurse 3 months after the patient's hospitalization, and infection from the patient was suspected. Cornification of the patient's soles and marked hypertrophy of the nails of both feet were observed. After a large number of scabies mites were detected on microscopic examination, crusted scabies was diagnosed. The patient was given oral ivermectin, 6 mg, once per week for 3 weeks, and crotamiton topical ointment containing 30% benzyl benzoate was applied on the body from the neck down. However, because a large number of scabies mites were detected again on microscopic examination, the dose of ivermectin was increased to 12 mg and administered 3 times. One week after the sixth dose of ivermectin was administered, hemorrhagic scabs around the mouth and erosion of the tongue developed. Mucosal drug eruption was suspected, and eruptions around the mouth and on the tongue resolved within 1 week after ivermectin being discontinued. 1% gamma-benzene hexachloride ointment was applied topically on the body from the neck down once a week, crotamiton ointment containing benzyl benzoate was applied daily, and the hypertrophic parts of the nails were removed. The patient subsequently achieved a full recovery.