Fungal infections of the nails

Fungal infections of the nails

What is a fungal infection of the nail?

Fungal infections of the nails are also known as dermatophytic onychomycosis, or tinea unguium. The responsible fungus is usually the same as that that causes athlete’s foot – a common infection of the skin of the feet, especially between the toes. In athlete’s foot the responsible fungus lives in the keratin that makes up the outer layer of the skin. When the fungus spreads to the keratin of the nails, the result is a fungal nail infection.

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What does it look like?

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Main body location

Foot, Hand


Can it appear anywhere?



What causes fungal infections?

Fungi spreading from athlete’s foot (known as ‘dermatophyte fungi’) cause most fungal nail infections. Less often a nail infection is due to other types of fungi, usually yeasts (eg. Candida) and moulds which do not cause athlete’s foot. These other fungi tend to attack nails that are already damaged, as it is easier for the fungus to invade. Fungal infections of the toenails are very common (1 in 4 people can be affected at a given time), those of fingernails less so. Both are seen most often in the elderly, those with impaired immune systems, and in people with diabetes and poor peripheral circulation. Warm, moist environment helps fungi to grow and cause infection. Wearing occlusive footwear or using shower stalls, bathrooms or locker rooms can increase the risk of fungal infections.

Are they hereditary?

Generally speaking, no. However, in some extremely rare cases there is a genetic risk factor and other family members can also be affected.

What are the symptoms of fungal infections of the nails?

At the start, there are usually no symptoms. Later the nails may become so thick that they hurt when they press on the inside of a shoe. They are then hard to trim. The look of an infected nail, particularly a fingernail, may cause embarrassment. The abnormal nail can damage socks and tights, and may cut into the adjacent skin. The skin nearby may also have a fungal infection; it may itch, crack, form a blister or appear white, especially between the toes.

What do fungal infections of the nails look like?

When fungi infect a nail, they usually start at its free edge, and then spread down the side of the nail towards the base of the cuticle. Eventually the whole nail may be involved. The infected areas turn white or yellowish, and become thickened and crumbly. Less commonly there may be white areas on the nail surface. The nails most commonly affected by fungal infections are those on the big and little toes. Sometimes, especially in those who carry out regular wet work such as housewives or cleaners, the skin around the fingernail becomes red and swollen. This is called paronychia, and can allow infection to get to the nail.

How are fungal infections of the nail diagnosed?

Fungal nail infections are usually diagnosed clinically. Your doctor may take a piece from the abnormal nail and send it to the laboratory to check if fungus can be seen under the microscope or grown in culture (this takes several weeks). Sometimes, repeated samples may be required. Many nail problems can look like a fungal infection – for example the changes seen in psoriasis, after a bacterial infection or an old injury – however, antifungal tablets will not help them. The right treatment may depend on knowing which fungus is causing the trouble; it can take several weeks to get culture results.

Can fungal infections of the nails be cured?

Yes. However, to successfully cure fungal toenail infection requires long treatment and may take up to a year. Fingernails are easier to treat. Fungal nail infections commonly recur, especially on the toes.

How can fungal infections of the nails be treated?

Fungal infections of the nail do not clear up by themselves, but not all of them need treatment. Some people with infected toenails are not bothered by them at all. In that case, they can sometimes be left alone (although the patient should remain cautious and try not to spread the infection to other parts of the body and nails or other people). On the other hand, if infected nails are embarrassing or uncomfortable then they are usually treated. It is important to treat people whose infections may cause significant health problems such as those with diabetes or immune suppression, in order to prevent potentially serious health problems.

The aim of the treatment is to get rid of the fungus: the nail will then usually return to normal. However, if the nail was abnormal before it was infected, it will be harder to clear and may just go back to its former state. Nail infections caused by moulds and yeasts can be very resistant to treatment.

Treatments applied to the nail (topical treatments)

Treatments applied to the nail work less well than those taken by mouth. They are most effective if the infection is treated at an early stage. The treatments used most often are amorolfine nail lacquer and tioconazole nail solution. Alone, they may not be able to clear the deeper parts of an infected nail, though regular removal of abnormal nail material with clippers or filing can help with this. Used in combination with an antifungal remedy taken by mouth, they increase the chance of a cure. They may have to be used for a period of 4 to 12 months before a response is noted. The course of treatment is shorter for fingernail infections. The cure rate with topical agents alone, is low, approximately 15-30%. Topical treatments are safe. Local redness and irritation can occur.

Treatment by mouth (oral treatments)

Before starting on tablets, the doctor should send a piece of the nail to the laboratory to check that the diagnosis of a fungal infection is confirmed.

Are there any side effects from the treatments?

Oral treatments are more likely to cause side effects than topical ones. Terbinafine occasionally causes a potentially very severe allergic reaction, can make some skin conditions worse, and rarely affects the sense of taste permanently. Itraconazole cannot be taken by people who are already taking some medicines. Your doctor will advise you about that. Both terbinafine and itraconazole can affect the liver, and your doctor may arrange blood tests to check this before and during treatment.

Although griseofulvin is the only licenced treatment in children, many dermatologists might use terbinafine as it is much more effective.

How will I know if the treatment is working?

The new nail will grow slowly outwards from its base, and it may be 6 months to a year after the treatment has finished before the nails look normal again. Fingernail infections clear up more quickly and completely than toenail ones; it can take 18 months for a toenail infection to grow out completely.


Surgical removal of nails

Sometimes very thick nails that are not likely to respond to tablets alone may have to be removed by surgeons under a local anaesthetic, however this is rarely performed since cure rates are not high enough to justify the discomfort of the surgery.

Self care (What can I do?)

  • Keep your nails short, dry, and clean. Stick to one nail clipper for the infected nails and another for the normal ones.
  • Don’t just treat your nails; use an antifungal cream to treat the skin that has athlete’s foot as well.
  • Avoid cutting the cuticle, either yourself or by a manicurist, since this increases the risk of nail damage and infection.
  • For toenail fungal infection:
  • Wear well-fitting shoes, without high heels or narrow toes.
  • Keep your feet dry, wear cotton socks, changed daily, and use ‘breathable’ shoes. Normal laundry in hot water clears most of the affected socks, but it can be made more effective if an antifungal spray can be used before laundry. Other clothes would not be infected by laundry with or without antifungal spray.
  • Maintain good foot hygiene, including treating any athlete’s foot
  • Wear clean shower shoes when using a communal shower.
  • Be meticulous with the hygiene of affected feet.
  • Consider seeking treatment from a podiatrist if thickened toenails cause discomfort when walking.

Image DermNetNZ

This information is provided by the British Association of Dermatologists.

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