Trichomycosis axillaris is a relatively common superficial bacterial colonization of the axillary hair shafts. Granular concretions, which are yellow, black, or red, adhere to the hair shaft and clinically characterize this condition. Trichomycosis axillaris is a benign disease with no associated mortality or complications. No racial predilection exists. Concretions encircle the hair shaft, making it appear beaded or thicker.
Concretions are most common on the central portion of axillary hair.
The insoluble cement substance elaborated by the bacteria adheres to the hair shaft and, occasionally, invades and destroys cuticular and cortical keratin. Black and red are seen most commonly in tropical climates. The hair shaft may become brittle and thus, more easily broken, but this is rare. Typically, since the hair shaft is not weakened, alopecia is not seen. The underlying skin usually is normal, although hyperhidrosis of the affected regions is common.