A 40-year-old man presented with axillary odor and reported having had dirty axillary hair for 4 years. The condition worsened in the summer, staining his clothing. His medical history was notable only for obesity. On examination, creamy yellow concretions were observed along several hair shafts (Panels A and B). The concretions took on a soft fluorescence when examined under a Woods lamp, but the skin of the axilla showed no coral red fluorescence, ruling out erythrasma. Microscopical examination after topical administration of potassium hydroxide showed an opaque material surrounding the involved hair, without invasion of the hair cortex (Panel C). The patient received a diagnosis of trichomycosis axillaris. Treatment consisted of shaving the affected hair and administering topical 15% aluminum chloride and topical erythromycin. The odor resolved within several weeks. Trichomycosis axillaris is a superficial bacterial infection that is typically caused by Corynebacterium tenuis. The adherent concretions on the hair shaft may be yellow, black, or red, and there is typically an associated rancid, acidic odor, which is due in part to the bacterial metabolism of testosterone in the apocrine sweat into malodorous compounds. Obesity, hyperhidrosis, poor local hygiene, and warm, moist environments are common predisposing factors.
D.-L. Ma and S. Vano-Galvan