Trichomycosis Axillaris: Symptoms, Causes, and Treatment in the UK

Trichomycosis axillaris (also known as Trichobacteriosis) is a superficial bacterial infection that affects the hair shafts in the underarm (axilla) and, less commonly, the pubic region. Despite its name, which suggests a fungal origin (mycosis), it is actually caused by an overgrowth of Corynebacterium species. These bacteria thrive in warm, moist environments, making the human armpit an ideal breeding ground.

Patients typically notice small, granular nodules that attach to the hair, making it appear thicker or 'beaded'. While the condition is physically harmless, it can cause significant distress due to its appearance and the strong, unpleasant odour (bromhidrosis) that often accompanies it. In the UK, this condition is frequently seen in gym-goers, manual workers, or individuals who struggle with excessive sweating, known as hyperhidrosis.

Visual Appearance

The hallmark of trichomycosis axillaris is the presence of yellow, red, or black concretions that adhere to the underarm hair. Yellow is the most common variety observed in the UK, while red and black nodules are more frequently reported in tropical climates. These nodules are usually 1–2mm in size and can make the hair feel brittle or sticky.

Odour and Staining

• Strong Odour: The bacteria break down sweat into malodorous compounds, leading to a persistent smell that standard deodorants may fail to mask.
• Sweat Discolouration: Patients often report that their sweat stains the underarms of white shirts yellow, orange, or even red.
• Skin Irritation: While the infection is confined to the hair shaft, the surrounding skin can sometimes become slightly irritated due to the associated moisture and bacterial load.

The primary cause is a species of bacteria called Corynebacterium tenuis. These bacteria are part of the normal skin flora for many people but can proliferate uncontrollably under specific conditions. Factors that increase your risk in the UK include:

• Poor Hygiene: Failing to wash the underarms regularly allows sweat and bacteria to accumulate.
• Hyperhidrosis: Excessive sweating provides the moist environment necessary for bacterial growth.
• Humidity: While the UK has a temperate climate, high humidity during summer months or in specific work environments can trigger outbreaks.
• Hirsutism: Having a larger volume of underarm hair provides more surface area for the bacteria to colonise.

In most cases, a UK GP or an online doctor can diagnose trichomycosis axillaris through a visual examination. The appearance of the nodules on the hair shaft is quite distinct. If you choose to speak to a GP online, high-quality photographs of the affected area are usually sufficient for a diagnosis.

In some clinical settings, a Wood's lamp (UV light) may be used; under this light, the yellow nodules may show a pale yellow or orange fluorescence. If the diagnosis is unclear, a microscopic examination of a plucked hair (using potassium hydroxide) or a bacterial culture may be performed to rule out fungal infections like tinea axillaris or erythrasma, which is another Corynebacterium-related skin condition that causes reddish-brown patches.

Treatment is generally straightforward and yields quick results if following NICE clinical guidelines for skin infections. Many patients find relief through a combination of the following:

1. Shaving the Area

The fastest way to eliminate the infection is to shave the affected underarm hair. Since the bacteria are physically attached to the hair shaft, removing the hair removes the colony. Shaving should be repeated for several weeks to ensure the bacteria do not recolonise new growth.

2. Topical Antibiotics

If shaving is not preferred or if the infection persists, topical treatments are used. These usually include Clindamycin or Erythromycin creams or lotions, applied twice daily for one to two weeks. Fusidic acid is another common option prescribed by UK doctors.

3. Antiseptic Washes

The use of benzoyl peroxide washes or Hibiscrub (chlorhexidine) can help reduce the bacterial load on the skin surface. These are often used as a preventative measure following successful treatment.

If you notice persistent changes to your underarm hair or a strong odour that does not improve with standard hygiene, it is worth seeking medical advice. An online doctor UK service is often the most convenient route for this condition, as it is easily diagnosed via photo consultation.

You should consult a professional if:

• Over-the-counter antiseptic washes have failed to clear the nodules.
• The skin in the armpit is becoming red, painful, or inflamed.
• The odour is affecting your self-esteem or social interactions.
• The nodules are spreading to the pubic area.

An online GP can provide an initial assessment and, if appropriate, issue a private prescription for topical antibiotics to be collected at your local pharmacy.

To prevent a recurrence of trichomycosis axillaris, consistency in hygiene is key. UK health experts recommend:

• Washing daily with an antibacterial soap or a mild cleanser.
• Keeping the underarms as dry as possible; using a high-quality antiperspirant (containing aluminium chloride) can be helpful for those with hyperhidrosis.
• Wearing breathable, natural fabrics like cotton or linen, especially during the summer or when exercising.
• Regularly trimming or shaving underarm hair if you are prone to infections.