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Fungal nail infection

A fungal nail infection occurs when a fungus attacks a fingernail, a toenail, or the skin under the nail, called the nail bed.

Fungal nail infections are relatively common.

Fungi can attack your nails through small cuts in the skin around your nail or through the opening between your nail and nail bed.

Photo of toenail with fungal infection

Image © ISM/Phototake

In healthy people, a fungal nail infection probably won't cause serious problems. However, it may look unpleasant and damage your nail or nail bed.

A fungal nail infection could lead to more serious problems if you have diabetes or a weakened immune system.

Symptoms of fungal nail infection

A fungal nail infection can cause a nail to turn white, black, yellow or green.

Fungal nail infections are not usually painful at first, but left untreated the infection may spread and could cause complications, which include cellulitis skin infection, or osteomyelitis bone infection.

If the infection becomes painful, shoes may be uncomfortable to wear and tasks using the hands such as writing may hurt.

Causes of fungal nail infection

Athlete's foot is a fungal skin infection that can spread to affect toenails. The risk of developing athlete's foot is increased by having hot sweaty feet.

Candida is a fungal yeast infection that can affect the skin around the fingernails before affecting the nails.

Health conditions, including diabetes or psoriasis, may increase the risk of fungal nail infections as they can damage the nail or skin allowing infections to develop.

Biting the nails and use of artificial nails can increase the risk of fungal nail infections.

The risk also increases with age and among smokers.

The Society of Chiropodists and Podiatrists says there may also be evidence of infection from close contact with some animals, and associated with certain sports such as marathon running. Research has been carried out into whether some people's genes make them more likely to have fungal infections, but this remains unclear.

Treatments for fungal nail infection

A mild fungal nail infection may not require treatment.

If a doctor decides treatment may be necessary, a sample clipping of an infected nail may be sent for laboratory testing. This will help determine the type and cause of the infection before planning treatment.

Antifungal tablets or antifungal nail paint are the main treatments recommended for fungal nail infections. These may take some months to be effective. Nail paint on a toenail could take up to a year to work.

Antifungal tablets such as terbinafine and itraconazole may cause side effects such as headache, itching, loss of taste, nausea or diarrhoea.

Preventing fungal nail infections

To help prevent fungal nail infections before and during any treatment, nails and feet need to be well looked after, including trimming nails short. A podiatrist can advise on good foot care.

Tips for good foot hygiene include:

  • Chose well-fitting footwear and socks that allow the feet to breathe and stay cool. Old shoes can harbour fungal spores from previous infections.
  • Use antifungal treatments on athlete's foot quickly to help prevent nail infections. Avoid picking up fungal infections in shared shower areas by using shower shoes.
  • Don't use the same nail scissors or clippers for infected nails and healthy ones.

WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on December 19, 2016

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