A fungal nail infection occurs when a fungus attacks a fingernail, a toenail, or the skin under the nail, called the nail bed.
Fungi (plural of fungus) can attack your nails through small cuts in the skin around your nail or through the opening between your nail and nail bed.
If you are healthy, a fungal nail infection probably won't cause serious problems. But it may look bad, hurt, or damage your nail or nail bed.
A fungal nail infection could lead to more serious problems if you have diabetes or a weak immune system. Talk to your doctor about the best way to treat a nail infection if you have one of these problems.
Often the infection is just in one nail, but several may be affected. At first the infection is usually painless. The nail may look thickened and discoloured (often a greeny-yellow colour). Commonly, this is all that occurs and it often causes no other symptoms. However, it can look unsightly.
Sometimes the infection becomes worse. White or yellow patches may appear where the nail has come away from the skin under the nail (the nailbed). Sometimes the whole nail comes away. The nail may become soft and crumble.
Bits of nail may fall off. The skin next to the nail may be inflamed or scaly. If left untreated, the infection may eventually destroy the nail and the nailbed, and may become painful. Walking may become uncomfortable if a toenail is affected.
Nail fungal infections are caused by microscopic organisms called fungi that do not require sunlight to survive. Most commonly, a group of fungi called dermatophytes (such as Candida) is responsible for nail fungal infections. However, some yeasts and molds also cause these infections.
Though Trichophyton rubrum is the most common dermatophyte that causes nail fungal infections, Trichophyton interdigitale, Epidermophyton floccosum, Trichophyton violaceum, Microsporum gypseum, Trichophyton tonsurans, and Trichophyton soudanense may also cause the infections. Common mold causes include Neoscytalidium, Scopulariopsis, and Aspergillus.
Pathogens that cause nail fungus infection usually enter the skin through tiny cuts or small separations between the nail and nail bed. The fungi grow when the nail provides a suitably warm and moist environment.
This is an option if the infection is mild or causing no symptoms. For example, a single small toenail may be infected and remain painless and of little concern.
Some people may prefer not to take treatment because:
- Treatment does not always cure the infection. Cure rates are about 60–80%.
- Treatment that clears the infection does not always restore the nail's appearance to normal.
- The antifungal drugs used for treatment need to be taken for several months, sometimes longer.
Although rare, unpleasant side-effects sometimes occur with antifungal drugs.
The option to treat can be reviewed at a later date if the infection becomes worse or if you change your mind.
However, treatment is usually advised if:
Symptoms are troublesome. For example, if walking is uncomfortable due to an affected nail.
Abnormal-looking nails cause distress.
You have diabetes, vascular disease, or a connective tissue disorder (because of a higher risk for secondary bacterial infections and cellulitis).
The nail infection is thought to be the source of a fungal skin infection on your body.
You are, or are likely to develop, severe problems with your immune system. For example, if you are to have certain types of cancer treatment.
Antifungal tablets will often clear a fungal nail infection. The medication will also clear any associated fungal skin infection, such as athlete's foot. Your doctor will usually recommend one of the following two drugs. The one chosen may depend on the type of fungus causing the infection. Both of these drugs cause side-effects in a small number of people, so read the packet that comes with the drug for a full list of cautions and possible side-effects.
Terbinafine tablets. The usual adult dose is 250 mg once a day; for between 6 weeks and 3 months for fingernails, and for 3–6 months for toenails. Visible improvement can be expected after the end of two months of treatment for fingernails and three months of treatment for toenails.
Itraconazole tablets. This is usually given as 'pulsed' treatment. That is, for an adult: 200 mg twice a day for one week, with subsequent courses repeated after a further 21 days. Fingernail infections require two pulsed courses and toenail infections require at least three pulsed courses.
Studies suggest that in about 5 in 10 cases the nail will look fully normal again after treatment. In about a further 2 in 10 cases the fungus will be cleared from the nail after treatment, but the nail does not look fully normal again. Fingernails tend to respond better to treatment than toenails. One reason for treatment to fail is because some people stop their medication too early.
Antifungal nail paint (nail lacquer)
A nail lacquer that contains the antifungal drug amorolfine is an alternative for most (but not all) types of fungi that infect nails. You can buy amorolfine nail lacquer from pharmacies as well as get it on prescription. However, this tends not to work as well as medication taken by mouth. Your doctor will advise if it is a suitable option for your type of infection. For example, it may be useful if the infection is just towards the end of the nail. This treatment does not tend to work so well if the infection is near the skin, or involves the skin around the nail.
The nail lacquer has to be put on exactly as prescribed for the best chance of success. You may need six months of nail lacquer treatment for fingernails, and up to a year for toenails.
If other treatments have failed, an option is to have the nail removed by a small operation done under local anaesthetic. This is combined with treatment with antifungal medication.
What to look out for with treatment
The fungi that are killed with treatment remain in the nail until the nail grows out. Fresh, healthy nail growing from the base of the nail is a sign that treatment is working. After you finish a course of treatment, it will take several months for the old infected part of the nail to grow out and be clipped off. The non-infected fresh new nail continues growing forward. When it reaches the end of the finger or toe, the nail will often look normal again.
Fingernails grow faster than toenails, so it may appear they are quicker to get back to normal. It may take up to a year after starting treatment before toenails look completely normal again and six months for fingernails to look completely normal.
Consult a doctor if there does not seem to be any healthy new nail beginning to grow after a few weeks of treatment. However, the infection can still respond to treatment even after you finish a course of medication. This is because the antifungal medication stays in the nail for about nine months after you stop taking medication.