Fungal nail infection: what it looks like, why testing matters and how it is treated

What it is and what it looks like

Fungal nail infection (onychomycosis) is a long-lasting infection that slowly damages the nail. It is most often caused by the same fungi that cause athlete's foot, a fungal infection of the skin of the feet. Toenails, especially the big toenail, are affected much more often than fingernails. The infection does not clear up on its own and can spread to other nails.

The change usually starts at the free edge of the nail and slowly moves towards its base. The nail may turn yellow, white or darker, become thicker and brittle, and crumble. Flaky debris builds up underneath, and sometimes the nail lifts off the nail bed. The infection is usually painless, but a thickened nail can press when you walk or wear tight shoes, and the skin around it sometimes becomes red.

Why the diagnosis needs to be confirmed

Other conditions can cause similar nail changes: psoriasis, an injury to the nail, lichen planus, a wart under the nail or a bacterial infection. Rarely, a nail change turns out to be a tumour, such as a melanoma. The appearance of the nail alone does not always show for certain whether the cause is a fungus.

That is why a sample is usually taken before long treatment, especially with tablets: small pieces of the affected nail and the debris under it are sent to a laboratory. The test shows whether a fungus is present and which type, which helps in choosing treatment. Results can take several weeks.

Who is more prone to it

The risk rises with age, and the infection is rare in children. People with diabetes, poor circulation in the feet or hands, or a weakened immune system, for example because of an illness or medicines, are more prone to it. Athlete's foot, psoriasis, heavy sweating and previous nail injuries also play a part.

Fungi thrive in warmth and moisture: sweaty feet in closed shoes or trainers, synthetic socks, walking barefoot in shared showers, changing rooms and around pools. The infection can also spread through shared towels, shoes and nail clippers.

Treatment options

Trimming and filing the nail do not remove the fungus on their own, because it lives in the nail and in the tissue beneath it. For a mild infection affecting less than half of the nail, antifungal lacquers and solutions applied to the nail may be used. They are usually applied for 6 to 12 months and work less well than tablets.

For more extensive infection, especially of the toenails, antifungal tablets are usually needed. They are prescribed by a doctor, because they can interact with other medicines and are not suitable with some liver or kidney diseases, or during pregnancy and breastfeeding. Blood tests are done before and sometimes during treatment. When a nail is badly affected, removing it is sometimes considered.

Even once the fungus has gone, the changed nail remains until new nail grows out. Fingernails clear faster; for toenails it can take a year or longer. A sign of success is healthy nail growing from the base. The infection often comes back, even after successful treatment, and if the nail was badly damaged, some changes may remain.

How to lower the risk

Treat athlete's foot promptly. Keep your nails short, clean and dry, and use separate clippers for the affected nail. Wear cotton socks and change them every day. Do not wear the same shoes two days in a row, and let them dry out. Wear flip-flops in shared showers, changing rooms and around the pool. Do not share towels, shoes or nail clippers.

Because the infection often comes back, these habits matter after treatment ends as well. If thickened toenails hurt when you walk, a podiatrist can help.

When to book an appointment

Book an appointment if you are not sure the nail change is fungal; if the nail hurts or gets in your way; if the infection is spreading to other nails; if pharmacy products have not helped; or if you have diabetes, poor circulation or a weakened immune system.

To book, call the Dermatologicum reception and ask for an appointment with Dr. Kraevska.