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Fungal Infections

podologist is a woman using a laser to treat onychomycosis - a fungal nail disease.

How common is a fungal infection?

It depends on where you live. In Canada it has been reported that almost 10% of the population has a fungal nail infection..¹

It is more common in people with certain conditions² such as

  • Diabetes

  • Circulation problems

  • Damaged nails

Signs and symptoms of a fungal nail infection

A fungal nail infection may not cause any obvious symptoms at first.

As it progresses, the infection can cause:

  • discolouration of the nail – it may turn white, black, yellow or green

  • thickening and distortion of the nail – it may become an unusual shape or texture and be difficult to trim

  • pain or discomfort – particularly when using or placing pressure on the affected toe or finger

  • brittle or crumbly nails – pieces may break off and come away completely

Sometimes the skin nearby may also become:

  • infected

  • itchy

  • cracked

  • red

  • swollen

What causes a fungal nail infection

Most fungal nail infections occur as a result of the fungi that cause athlete's foot infecting the nails (Tinea).

These fungi often live harmlessly on your skin, but they can sometimes multiply and lead to infections. The fungi prefer warm, dark and moist places like the feet.

They can enter the nail in a variety of ways:

  • under the edge of the nail where it attaches to your toe

  • directly through the top surface of the nail

You're more likely to get a fungal nail infection if you:

  • don't keep your feet clean and dry

  • wear shoes that cause your feet to get hot and sweaty

  • walk around barefoot in places where fungal infections can spread easily, like communal showers, locker rooms and gyms

Fungal nail infections can be spread to other people, so you should take steps to avoid this if you have an infection.

Treating a fungal nail infection

A fungal nail infection is unlikely to get better without treatment. However, if you're not bothered by it you might decide it's not worth treating because treatment:

  • can take a long time

  • can cause side effects

  • isn't always effective

Treatment may also be unnecessary in mild cases of fungal nail infection. It's also unlikely to cause any further problems so you may feel it's not worth treating.

For more severe or troublesome fungal nail infections, antifungal medication may be recommended.

Antifungal medication comes in tablets or a special paint you apply directly to the nail.

A small sample of the infected nail may need to be taken and sent off for testing before treatment starts, to confirm that you do have a fungal infection.

If the treatment is working, you should see a new healthy nail start to grow from the base of nail over the course of a few months. The old infected nail should begin to grow out and can be gradually clipped away.

Antifungal treatments are thought to be effective in treating about 60 to 80% of fungal nail infections. It can take between 6 and 18 months for the appearance of the affected nail to return to normal, and in some cases the nail may not look the same as before the infection.

Antifungal tablets

Terbinafine and itraconazole are the 2 medicines most commonly prescribed for fungal nail infections.

These usually need to be taken once or twice a day for several months to ensure the infection has completely cleared up. If you stop taking the medication too early, the infection may return.

Possible side effects of antifungal tablets can include:

Antifungal nail paint

If you prefer not to take antifungal tablets, your GP or pharmacist may suggest you try antifungal nail paint instead.

Nail paint isn't generally considered to be as effective as tablets because it can be difficult for it to reach the deeper layers of the nail. However, it doesn't usually cause any side effects.

Like antifungal tablets, antifungal nail paint also normally needs to be used for several months to ensure that the infection has cleared up.

How to prevent fungal nail infections

Whether or not you decide to have treatment, you should still follow self-help advice to help stop the condition getting worse or spreading to others.


  • keep your hands and feet clean and dry

  • wear well-fitting shoes made of natural materials and clean cotton socks – these will allow your feet to "breathe"

  • clip your nails to keep them short – don't share clippers or scissors with other people

  • replace old footwear that could be contaminated with fungi

  • treat athlete's foot as soon as possible to avoid the infection spreading to your nails

  • ensure your towels are washed regularly

  • make sure any equipment is properly sterilised between uses if you visit a nail salon


  • do not share towels and socks with other people

  • do not walk around barefoot in public pools, showers, and locker rooms – special shower shoes are available to protect your feet

Onychomycosis can be difficult to diagnose based on physical appearance and clinical history alone. Clinicians should confirm a diagnosis of onychomycosis by laboratory testing before prescribing antifungal medications. The following types of laboratory tests can confirm the diagnosis of onychomycosis:

  • Microscopy: Potassium hydroxide (KOH) stain can be performed in the office setting, but the accuracy of the test depends on clinician experience and technique. Nail clippings or scrapings are placed in a drop of KOH and examined under a microscope for the presence of fungal elements.³

  • Histopathologic examination with a periodic acid-Schiff (PAS) stain: Examination of nail clippings with a PAS stain can confirm the diagnosis of a fungal nail infection.

  • Culture:Fungal culture can be used to identify the infecting organism, but the fungi may take several weeks to grow. ,

  • Molecular: Molecular testing, including polymerase chain reaction (PCR) testing, may be used to diagnose fungal nail infections.

Antimicrobial-resistant onychomycosis is a growing problem.¹³⁻¹⁵ Therefore, antifungal susceptibility testing may be considered based on the fungus or fungi identified and the patient’s clinical course.¹²,¹⁶,¹⁷

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