Onychomycosis is an infection of the nail caused by a fungus. The infection occurs more often on toenails than fingernails.

Fungal Infection of the Toenails

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The fungi that cause onychomycosis thrive in warm, moist environments. Factors that may contribute to onychomycosis include:

  • Injury to the nail
  • Exposure to warm, moist environments, like locker rooms
  • Damp socks
  • Tight fitting shoes
  • Poor nail care

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

Risk factors for onychomycosis include:


Onychomycosis can affect one or more nails.

Symptoms include:

  • Thickened nail that is difficult to cut
  • Brittle or ragged nail
  • Discolored or unsightly nail
  • Pain of the finger or toe with ordinary activities


Your doctor will ask about your symptoms and medical history, and perform a physical exam. You may need to be referred to a doctor who specializes in skin and nail disorders (a dermatologist). The doctor may scrape or clip the nail to send a sample for testing.

Tests on the nail sample may include:

  • Culture
  • Microscopic examination


Since nails grow slowly, it can take up to a year to have a completely clear nail. Onychomycosis can be difficult to treat and may return after treatment. Talk with your doctor about the best treatment plan for you. Treatment options include the following:


  • Prescription antifungal medications taken by mouth (Note: Some people cannot take antifungal medications. Tell your doctor about any other medications you are taking and any medical problems you have.)
  • Creams and ointments
  • Antifungal nail lacquer


Surgery to remove the nail is sometimes performed in severe cases of onychomycosis. A new nail grows in its place.


To help reduce your chance of getting onychomycosis, take the following steps:

  • Keep your feet clean and dry them completely after washing.
  • Keep your hands dry and wear rubber gloves when cleaning.
  • Keep nails short and clean, trimming them straight across.
  • Do not trim or pick at the skin near your nails.
  • Take care to avoid injuring your toenails.
  • Avoid shoes that are too tight.
  • Wear absorbent cotton socks and change them if they become damp.
  • Avoid walking barefoot around swimming pools, locker rooms, and other public places.
  • Choose a reputable salon for manicures and pedicures.
  • Avoid artificial nails, which can trap moisture.
  • Stop smoking.
  • If you have diabetes, see your doctor about steps you can take to better control your blood sugar.