Overview of Toenail Fungus

Do You Have Thick, Yellowed Toenails?

Close up of dry toe with yellowed nail fungus
All About Toenail Fungus. Ziga Lisjak / Getty Images

Toenail fungus, also known as onychomycosis, is a fairly common condition that disfigures and can destroy the toenail. The big toe and the little toe are the nails that are most likely to be affected. Onychomycosis is caused by any one of the many types of fungi that grow in the warm, moist environment in your shoes. As the fungi grow, they invade and feed on the protein (keratin) that make up the hard surface of the toenails.

Toenail fungus is rare in children, but the incidence increases as you age, with an estimated 48% of people in the United States having at least one toe affected by the time they are 70.

Wearing tight-fitting shoes and layers of nail polish increase the risk of developing toenail fungus. It can also be spread person-to-person in public areas, such as locker rooms and showers. Having a chronic condition that affects your circulation, such as diabetes or HIV, also increases your risk.

Symptoms of Toenail Fungus

The affected nail will become discolored (yellow or brown) and will become very thick and overgrown. You may notice foul-smelling debris under the nail, which may crumble and eventually completely fall off, or it may become so thick that it is very painful to wear shoes.

Diagnosis of Toenail Fungus

If a fungal infection becomes uncomfortable enough to seek medical treatment, your doctor will examine the toenail and may take small samples.

The nail can be examined for fungi or some other infection under a microscope in the lab.

Treatment of Toenail Fungus

Toenail fungus often becomes a chronic condition, and if it is not painful, many people do not get treatment. But people with chronic illnesses like diabetes should see a doctor if they notice changes in their nails, as it may be an indication of more serious problems.

If the nail becomes very thick and makes wearing shoes and walking painful, you should see a doctor.

The nail can be trimmed and filed down carefully, either at home or by a foot specialist (podiatrist). If the infection is mild and very localized, your doctor may prescribe a medicated nail polish containing either Loceryl (amorolfine) or Loprox (ciclopirox).

If the infection persists or continues to spread, your doctor may prescribe an oral, systemic anti-fungal medication such as Sporanox (itraconazole) or Lamisil (terbinafine). The length of treatment will be about 12 weeks. Both of these drugs have some very serious side effects and may not be appropriate for some people.

For extremely persistent infections, permanent surgical removal of the nail may be necessary.

Prevention of Toenail Fungus

You can help to prevent toenail fungus by:

  • Wearing comfortable, well-fitting shoes and clean hosiery every day, and allowing your shoes to dry thoroughly between wearings
  • Wearing shower shoes, sandals or flip-flops in community showers or locker rooms
  • Washing your feet daily, drying them thoroughly, and using a good-quality foot powder
  • Keeping your toenails trimmed
  • Avoid applying layers of nail polish

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