Trichomycosis, also known as trichobacteriosis, is a bacterial infection that mainly occurs in the underarm hairs. In rare cases, the infection can occur elsewhere, such as in the pubic hair or the hair between the buttocks.

The main symptom of trichomycosis is colored nodules on the hair shaft, which may make the hair appear thicker. However, some people experience no symptoms from the infection.

Anyone who suspects that they have trichomycosis should see a doctor or dermatologist for a diagnosis.

Some people may need antibiotics to treat trichomycosis.

In this article, we discuss trichomycosis and its associated symptoms and treatments. We also look at good hygiene practices and when to get advice from a doctor.

Trichomycosis is a bacterial infection that happens due to an overgrowth of types of bacteria called Corynebacterium.

Corynebacterium grows most efficiently in moist areas of the body, such as the:

  • armpits
  • groin
  • space between the buttocks

The specific name for trichomycosis changes depending on the area that the bacteria infect. For instance, trichomycosis axillaris occurs in the underarms, whereas trichomycosis pubis develops in the pubic hair.

Trichomycosis is most common in the underarm hair. A review in the International Journal of Trichology notes that of 56 confirmed trichomycosis cases, 97.4% occurred in the underarms. The infection of other areas was rare.

A trichomycosis infection causes nodules, which stick to the hair shaft, where they grow and multiply.

These nodules are most commonly yellow, with red and black nodules occurring less frequently.

As the nodules can be one of the only symptoms, many people do not notice that they have an infection. Over time, the infection can become chronic, and the symptoms may become more noticeable and uncomfortable.

Treatment for trichomycosis is usually straightforward.

The nodules that the bacteria create adhere to the shaft of the hair with a strong adhesive substance, which makes them challenging to remove.

Treatment typically begins with shaving the affected hairs and the surrounding area to remove as much of the bacteria as possible.

Doctors may then prescribe topical antibiotics, such as erythromycin or clindamycin. They may also recommend a cream or ointment that contains benzoyl peroxide.

If the topic antibiotics do not work, or the infection keeps returning, doctors may prescribe an oral antibiotic. However, trichomycosis infections are superficial, and most are treatable using topical methods.

Following good hygiene practices is an important part of both treatment and prevention for trichomycosis. Proper hygiene may help get rid of unwanted bacteria and keep them from coming back.

Good hygiene practices include:

  • washing the affected area every day with soap and water
  • wearing breathable clothing to allow airflow to the area
  • avoiding tight fitting or synthetic clothing that may hold moisture in the area
  • using talc-free powder, such as baby powder, to keep the area dry and prevent moisture buildup
  • drying the body thoroughly after bathing or swimming

Doctors may also recommend that people who sweat profusely use an antiperspirant deodorant to block extra sweat from their underarms.

The symptoms of a trichomycosis infection can vary.

Some people have no noticeable symptoms, and doctors may only find the infection after close inspection.

Others may notice the characteristic yellow, red, or black nodules that stick to the hair shaft. People may also see changes in the texture of the underarm hair.

Other changes that could indicate trichomycosis include:

  • foul-smelling or acidic sweat
  • excess sweat in the affected area
  • prominent sweat stains on clothing
  • dark or off-color sweat
  • hair loss in the affected area

These symptoms are a sign to see a doctor or dermatologist for a diagnosis. There are no long-term complications from the infection, but early treatment may make it easier to treat.

A trichomycosis infection occurs when Corynebacterium grow and multiply in an area. Once these bacteria attach themselves to the hair shafts, they can be tough to remove and may increase further, causing an infection.

Trichomycosis is typically not contagious. However, researchers have noted cases of the infection passing from person to person in very close and overcrowded environments, such as among sports team members.

Sometimes, the infection may spread to more than one area of the body at a time. Early treatment is essential to prevent symptoms from getting worse or becoming uncomfortable.

Trichomycosis can affect anyone, but it is most common in areas of the world with warm, humid climates.

Other risk factors that may influence the infection include excessive underarm sweat, not shaving the area, and poor hygiene.

Trichomycosis appears to affect men more often than women, though this may be because women are more likely to shave their armpits.

Anyone who notices symptoms of trichomycosis should see a doctor for diagnosis and treatment. Other conditions may cause similar symptoms, so a thorough diagnosis is vital in each case.

Early treatment may make the infection easier to eliminate.

If a person receiving treatment has symptoms that do not go away or get worse, they should seek advice from their doctor.

Trichomycosis is a topical infection that occurs in moist areas of the body — most commonly, the armpits. Bacteria attach themselves to the hair shaft, producing nodules that are usually yellowish but can sometimes be red or black.

Symptoms are generally mild or slightly uncomfortable. Trichomycosis typically responds well to treatment.

Good hygiene practices to keep the area clean and dry may help prevent further infections.