Fungal nail infections

Most fungal nail infections are caused by a type of fungus called dermatophytes. Dermatophytes are a type of mould fungus that also cause athlete's foot (tinea pedis), which affects the skin between the toes or on the soles of the feet. Athlete's foot can spread to the toenails. 

Less commonly, fungal nail infections can be caused by yeasts, like Candida, or non-dermatophyte moulds. Yeast infections often affect fingernails and can happen when fingernails become damaged by excessive hand washing or wet work. 

Some things increase the chance of getting a fungal nail infection: 

• Warm, moist environments, like sweaty feet in closed shoes or trainers 
• Socks made from synthetic materials that trap sweat 
• Shared showers, bathrooms, or gym changing rooms 
• Repeated nail injuries from sports or fitness activities 

Are fungal nail infections hereditary?

Fungal nail infections are not directly passed down in families, but living with someone who has an infection can make it easier to catch. 

Rarely, fungal nail infections seem to be more common in some families. This might be due to rare genetic differences in the immune system or nail growth, which make fungal nail infections easier to get or harder to treat. 

Fungal nail infections usually start at the end of the nail and grow towards the base (the nail matrix; where nails grow from). They can also start at the side of the nail or under the cuticle if it is damaged. 

Early signs include: 

• Colour changes – parts of the nail may turn yellow, white, or brown 
• Thickened nails that grow slowly 
• Crumbly or split tips 
• Flaky debris under the nail 
• Rough or bumpy nails that may hurt when pressed or in shoes 

As infections get worse, the nails may become hard, thick, or misshapen.  Permanent damage can occur if the nail matrix is affected. 

Image DermNetNZ.

Fungal nail infection can often be suspected by how the nails look. But other nail problems, such as psoriasis, can look very similar to fungal nail infection. Testing is often done to confirm the diagnosis. 

The commonest test is done by sending a piece of affected nail to a laboratory for assessment. Results can take several weeks to return, depending on how the testing is performed. 

Your healthcare professional may either take a clipping of the nail themselves or ask you to perform this. You may be supplied with a clean container or folded card to put samples in. The steps needed are: 

• Wash and dry your hands or feet well. A hair dryer, on a cool, jet, can be used to dry around and under the nail. 
• Use clean nail clippers to cut a tiny piece from the part of the nail that looks thick, crumbly, or discoloured. Clip as far back as you can without pain. Infected nails are often lifted up, making clipping easier. 
• If there are any flaky bits under the nail, you can gently scrape them off too. 
• Place any collected nail pieces into the supplied container or cardboard. 

Sometimes, the test does not work and you may need to have a repeat sample taken. Rarely, a dermatologist may take a biopsy of the nail, if the diagnosis is not confirmed. Some doctors and podiatrists use a rapid testing kit to identify the infection, on the day or within a day, where available. 

Should fungal nail infections be treated? 

Fungal nail infections do not always need to be treated. Some people leave them alone if the nail is not painful or causing problems. However, nail infections do not go away by themselves, and even if successfully treated, it is common for nails to become re-infected. 

Treatment should be considered if: 

• The appearance of the nails bothers you 
• Affected nails are painful or make it hard to walk, wear shoes, or use your hands 
• There is a risk of bacterial infection of the deeper layers of the skin (cellulitis) from cuts or cracks in the skin surrounding the nail or under the nail. Cellulitis can become serious, especially in people with diabetes, poor circulation, nerve problems, or weakened immunity. 

Can fungal nail infections be cured?

Treatment can kill fungus and cure an infection. This, however, does not guarantee any affected nails will return to their past normal appearance. This is particularly true in already badly damaged nails, or where the nail matrix has been infected and damaged by fungus. Despite clearing an infection, some degree of nail change may still be present. 

How can fungal nail infections be treated? 

There are different ways to treat fungal nail infections. Some treatments are put directly on the nail. Others are taken as tablets by mouth. Physical methods can also be used. These can remove infected material and make the nail more comfortable. In some mild cases, they can even clear the infection on their own. For some nail infections, combing all three approaches may help infections clear faster.  

Treatment options include:

Treatments applied on the nail:

Treatment by mouth:

Physical treatments:

Are there any side effects from the treatments?

Oral treatments are more likely to cause side effects than topical ones. Oral tablets can sometimes cause mild side effects such as nausea, upset stomach, bloating and headaches. 

Some people develop rashes. Most are harmless and disappear when the medicine is stopped. Very rarely, a medicine may cause a severe skin rash. This can be serious and life threatening. Severe rashes spread over the body with skin blistering and peeling, mouth, eye or genital soreness, and a feeling of being very unwell. 

Oral treatments can interfere with other medicines. Your healthcare professional will check that any medicines you take are not affected by an oral antifungal. 

Oral antifungals rarely affect the liver or bone marrow. Your doctor will usually perform a blood test before treatment to check these tablets can be safely used. Blood tests may need to be performed during treatment, to watch for any concerning changes. 

How will I know if the treatment is working?

Treatment success can be confirmed either by new and unaffected nail growingor, after treatment is completed, repeated nail testing for any remaining fungus. It is important to know that tablet antifungals stay in the nails for several months; testing too soon (within 3 months) of a course can give false results. 

• Keep your nails short, dry, and clean. Stick to one nail clipper for the infected nails and another for the normal ones. 
• In addition to your nails the affected skin (e.g. athlete's foot) must be treated with antifungal cream or solution as well. 
• Avoid cutting the cuticle, either yourself or by a podiatrist or 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 and change them daily. Choose breathable shoes. 
• Wash affected socks in hot water. You can spray them with antifungal spray before washing for better results. The infection will not spread to other clothes in the wash. 
• Do not wear the same shoes two days in a row. Let the shoes dry out between uses. 
• Shoes can be treated with antifungal sprays or powders to kill any fungus present. This can be repeated from time-to-time, for prevention. 
• Wear clean shower shoes or flips flops when using a communal shower or going to swimming pools. 
• Keep affected feet very clean. 
• When drying the feet, using a hairdryer on a cool jet can dry the skin between the toes. 
• Consider seeking treatment from a podiatrist if thickened toenails cause discomfort when walking.