Fungal Nail Infections (Onychomycosis): Symptoms, Causes, and UK Treatments

A fungal nail infection, medically known as onychomycosis, occurs when fungi overgrow in, under, or on the nail. While it can affect both fingernails and toenails, it is significantly more common in toenails due to the dark, warm, and moist environment provided by shoes and socks. In the UK, it is estimated that around 3 in 100 people will experience a fungal nail infection at some point in their lives.

These infections are usually not serious but can be persistent and difficult to treat without medical intervention. Because the fungus thrives on keratin—the protein that makes up the nail—the infection can lead to physical changes in the nail's structure over time. While it may start as a small white or yellow spot, if left untreated, it can spread deeper into the nail bed and even to other nails.

Fungal nail infections often develop slowly and may be painless in the early stages. However, as the infection progresses, you may notice several distinct changes to your nails:

• Discolouration: The nail may turn white, yellow, or brown. In some cases, it may appear green or black if secondary bacteria are present.
• Thickening: The nail often becomes much thicker than usual, making it difficult to trim.
• Brittleness: The nail may become crumbly, ragged, or brittle, with pieces breaking off easily.
• Distortion: The shape of the nail may change, or it may begin to lift away from the nail bed (onycholysis).
• Debris: Fungal debris may build up under the nail, often causing a slight odour.

If the infection is severe, the affected area may become painful, especially when wearing tight-fitting shoes or walking.

The infection is most commonly caused by a group of fungi called dermatophytes, which are also responsible for athlete's foot. When these fungi come into contact with the nail, they can enter through small cracks in the nail or the surrounding skin. Several factors can increase your risk of developing a fungal nail infection in the UK environment:

• Age: Older adults are more susceptible due to reduced blood flow and slower nail growth.
• Pre-existing conditions: People with diabetes, psoriasis, or a weakened immune system are at higher risk.
• Athlete's Foot: Having a fungal skin infection on the feet often leads to the fungus spreading to the toenails.
• Environment: Walking barefoot in communal showers, gyms, or swimming pools increases exposure to fungal spores.
• Footwear: Wearing tight, non-breathable shoes that cause feet to sweat creates an ideal breeding ground for fungi.

Fungal nail infections rarely clear up on their own and usually require targeted treatment. In accordance with NICE guidance, treatment is typically recommended if the infection is causing pain, discomfort, or social embarrassment. The main options available in the UK include:

Antifungal Nail Lacquers

For mild to moderate infections that haven't reached the root (lunula) of the nail, medicated nail lacquers containing Amorolfine or Tioconazole may be used. These are painted onto the nail usually once or twice a week. Note that this treatment requires patience, as it can take 6 months for fingernails and up to 12 months for toenails to clear.

Oral Antifungal Tablets

For more severe or stubborn infections, a GP may prescribe antifungal tablets such as Terbinafine or Itraconazole. These are more effective than lacquers because they treat the infection from within the bloodstream. However, they may involve side effects and require monitoring of liver function.

Nail Softening Pastes

Some over-the-counter kits involve using a urea-based paste to soften the infected part of the nail over several days, allowing it to be scraped away. This is then followed by antifungal cream applied to the exposed nail bed.

Once an infection has cleared, it is vital to take steps to prevent it from returning, as recurrence rates are high. Follow these evidence-based tips to keep your nails healthy:

• Keep feet clean and dry: Always dry thoroughly between your toes after washing.
• Choose the right footwear: Wear breathable shoes made of natural materials like leather, and change your socks daily.
• Use antifungal powder: If you are prone to sweaty feet, use an antifungal powder inside your shoes.
• Protect your feet in public: Wear flip-flops or shower shoes in gym changing rooms and pool areas.
• Sanitise tools: Disinfect nail clippers after each use and do not share them with others.
• Treat athlete's foot early: If you notice itchy, peeling skin between your toes, treat it immediately with antifungal cream to prevent it spreading to your nails.

While some mild fungal nail infections can be managed with over-the-counter treatments from a pharmacy, many cases require a professional assessment. You should consider booking a consultation with an online GP if:

• Over-the-counter treatments have failed to work after several months.
• The nail is becoming increasingly painful or makes walking difficult.
• The infection is spreading to other nails or the surrounding skin.
• You have underlying health conditions like diabetes or circulatory problems, as foot infections can lead to more serious complications.
• You are seeking a prescription for oral antifungal medication, which requires a clinical review.

An online GP can review photos of your nail, discuss your medical history, and advise on the most appropriate course of action, including private prescriptions or referrals if necessary.