Fungal nail infection: treatment, symptoms, causes and how long it takes to clear

The NHS describes a staged approach. Treatments from a pharmacy come first, and tablets are for when those have not worked. NICE CKS describes similar steps, starting with self-care and a topical option for early or limited infection, and says nail regrowth should be assessed 3 to 6 months after starting treatment.

The NHS and the British Association of Dermatologists (BAD) describe several options. The BAD says treatments applied directly to the nail work best for early infections where less than half the nail is affected, and are less effective than treatments taken by mouth. Often they are used together.

The NHS says the infection is cured when you see healthy nail growing back at the base, and that antifungal nail medicines may take several months before you see an improvement. The BAD says toenail infections may take 12 to 18 months to clear and fingernails 9 to 12 months, and that treatment success is confirmed by new unaffected nail growth or by repeat nail testing after treatment.

The BAD adds that tablet antifungals stay in the nails for several months, so testing within 3 months of a course can give false results. It also says that treatment can kill the fungus but does not guarantee the nail will return to its past normal appearance, particularly in badly damaged nails, and that it is common for nails to be re-infected.

The BAD says most fungal nail infections are caused by dermatophytes, the same type of mould fungus that causes athlete's foot, which can spread to the toenails. It says the infections are not directly passed down in families, but living with someone who has an infection can make it easier to catch, and that warm, moist environments, shared showers, bathrooms or gym changing rooms and repeated nail injuries increase the chance of getting one.

The NHS advises not sharing towels, nail clippers or scissors, not wearing other people's shoes, wearing flip-flops in gym or pool showers, and treating athlete's foot as soon as possible to avoid it spreading to the nails. The BAD advises using one nail clipper for infected nails and another for normal ones, and says the infection will not spread to other clothes in the wash.

A fungal nail infection, known medically as onychomycosis, is an infection of the nail by a fungus. NICE Clinical Knowledge Summaries explains that it can involve the nail plate, the nail bed and the root of the nail, and that the nail may discolour, the plate may become distorted, and the tissue under the nail may thicken.

The NHS says the infection usually starts at the edge of the nail and often spreads to all of it, making it thicker and turning it white or yellow. The nail may become brittle and crumbly, and the whole nail can sometimes lift off, leaving the skin around it swollen and painful.

It is far more common in the toenails than the fingernails. According to NICE CKS, toenails are seven times more likely to be affected, and dermatophytes, a group of moulds, are responsible for about 90% of cases, with yeasts such as Candida and other moulds making up the rest.

You can get a fungal nail infection if your feet are constantly warm and damp, according to the NHS, and you are more likely to if you wear trainers for a long time and have hot, sweaty feet. NICE CKS adds that it is more common in older people and athletes and is rare in children.

The same source lists the factors that raise the risk: a fungal skin infection elsewhere, psoriasis, diabetes, peripheral arterial disease, immunocompromised states, repeated nail trauma and occlusive footwear.

NICE CKS says a fungal nail infection should be suspected if the nail looks abnormal and discoloured, with white or yellow streaks along one side, thickening, white or yellow spots, or complete destruction of the nail. Redness and swelling of the skin fold beside the nail, called paronychia, may suggest Candida.

Other nail conditions can look similar, which is why a sample is sometimes taken. The NHS says that before giving tablets a GP might take a sample of the nail and have it tested to find out what type of infection you have. NICE CKS describes this as nail clippings or scrapings for microscopy and culture, and says it is arranged if the person wishes to start antifungal treatment.

Assessment also covers pain, difficulty with footwear and walking, the psychological impact, other conditions that raise the risk, and whether other family or household members are affected.

The NHS advises seeing a GP if the infection is severe and treatment has not worked, if it has spread to other nails, if you have diabetes (because foot problems can be more serious), or if you have a weakened immune system, for example after an organ transplant or during chemotherapy.

NICE CKS adds that referral to a podiatrist may be considered when thickened toenails cause discomfort walking, when footwear is causing trauma to the nail, or when deformed toenails are damaging adjacent toes. A dermatologist may be considered if the diagnosis is uncertain, if primary care treatment has failed, if there is another nail disease such as psoriasis or lichen planus, or if a child needs oral treatment.

The NHS lists things that help prevent infection: treat athlete's foot as soon as possible so that it does not spread to the nails, keep nails short, keep feet clean and dry, wear clean socks every day, wear flip-flops in showers at the gym or pool, wear shoes that fit well and do not have high heels or narrow toes, and throw out old shoes.

It also lists things not to do: do not wear shoes that make your feet hot and sweaty, share towels, wear other people's shoes, or share nail clippers or scissors.

Because a nail grows slowly, there is no quick fix: the NHS says it may take several months before you see any improvement from a nail paint. The key sign of success is clear nail growing from the base, not how the remaining damaged nail looks, which will grow out over time.

If treatment is unsuccessful, NICE CKS says measures include managing any underlying cause, resampling the nail, and combining a topical and an oral antifungal. Many people decide that the appearance of the nail does not justify long treatment, and that is a legitimate choice when there is no pain or other risk.

Most fungal nail infections are managed through a pharmacist or GP. A private podiatrist or dermatologist can examine the nail, take a sample and discuss options with shorter waiting times, and some may offer additional treatments. The NHS and NICE guidance cited here describe pharmacy treatments, tablets and nail removal, so it is worth asking any provider for the evidence behind anything else, what the course involves, and how success will be judged.