We report on a 65-year-old diabetic patient, who developed a deep fungal infection in the beard region after initial therapy with systemic antibiotics and topical corticosteroids. We were able to isolate Trichophyton mentagrophytes and treated him successfully with terbinafine 250 mg day(-1) orally in combination with topical ciclopirox and polyhexanide. In follicular inflammation in diabetics, deep mycosis has to be considered and mycologic diagnostics should be performed before starting any other treatment.