Fungal nail 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 (e.g. 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 with poor blood circulation in the hands and feet.

Warm, moist environments help fungi to grow and cause infection. For example, occlusive footwear, such as work boots, or socks or trainers made of synthetic materials, can cause the feet to sweat excessively (hyperhidrosis), which increases the risk of fungal infections. Further, shared shower stalls, bathrooms or locker rooms also pose a risk of spreading fungal infections

Are fungal nail infections hereditary?

No, however, in some extremely rare cases, there is a genetic risk factor and other family members can also be affected.

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.

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 toe. Sometimes, especially in those who carry out regular wet work such as cleaners, the skin around the fingernail becomes red and swollen. This is called paronychia, and can allow infection to get to the nail.

Image DermNetNZ.

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 nail infections be cured?

Yes. However, longer treatment is required, and it may take up to a year to successfully clear fungal toenail infection. Fungal nail infections commonly recur (come back), especially on the toes. Fingernails are easier to treat.

How can fungal nail infections be treated?

Fungal nail infections 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 make a person feel embarrassed or uncomfortable, then they can be 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 on the nail (topical treatments)

Treatments applied on 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. By themselves, these treatments may not reach the deeper parts of the 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, topical treatments increase the chance of complete clearance For toenails, they may have to be used for a period of 4 to 12 months before an effect is noted. The course of treatment is shorter for fingernail infections. The clearance 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.