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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z



Trichomycosis axillaris

Trichomycosis axillaris is a superficial bacterial infection of underarm hair. It is characterised by yellow, black or red granular nodules or concretions that stick to the hair shaft.

The name is misleading because trichomycosis is bacterial in origin rather than a fungal infection.

Trichomycosis axillaris
Black concretions
Trichomycosis axillaris
Black concretions
Trichomycosis axillaris
Yellow concretions
Trichomycosis axillaris

What causes trichomycosis axillaris and who gets it?

It is caused by the overgrowth of Corynebacterium (mostly Corynebacterium tenuis) and basically the concretions consist of tightly packed bacteria. They prefer moist areas of the body thus mainly affect underarm hair, and to a lesser extent, pubic hair (trichomycosis pubis).

Trichomycosis axillaris occurs in males and females of all races from both temperate and tropical climates. It appears to be more common in men than women but this is because many women shave their underarm hair.

What are the signs and symptoms of trichomycosis axillaris?

Usually the condition is symptomless and all that is noticed is sweaty smelly armpits. On closer inspection, 1-2 mm yellow, red or black concretions can be found encircling the hair shaft, making the hair appear beaded or thicker. Sweat may be coloured according to the colour of the concretions and may stain clothing. Yellow concretions are the most common, whilst red and black are seen most often in tropical climates. Rarely, bacteria may invade and destroy the hair shaft.

What is the treatment of trichomycosis axillaris?

Trichomycosis axillaris is a benign condition that does not have any complications. The fastest way to get rid of the problem is to clip the affected hairs or shave the area. Agents used to help treat and prevent the problem include benzoyl peroxide gel or wash formulations and topical antibacterial preparations of clindamycin or erythromycin. Antiperspirants are also useful because they reduce sweating. Keep the underarm clean and dry to prevent recurrences of the condition.

Related information

References:

Textbook of Dermatology. Ed Rook A, Wilkinson DS, Ebling FJB, Champion RH, Burton JL. Fourth edition. Blackwell Scientific Publications.

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Author: Vanessa Ngan, staff writer

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