Infection - fungal - nails

Alternative names
Nails - fungal infection; Onychomycosis; Fungal nail infection

This disease is an infection of the nails by a fungus.

Causes, incidence, and risk factors

The body normally hosts a variety of microorganisms, including bacteria and fungi. Some of these are useful to the body. Others may multiply rapidly and form infections. Fungi can live on the dead tissues of the hair, nails, and outer skin layers.

Fungal infections include mold-like fungi that cause:

  • athlete’s foot  
  • jock itch  
  • ringworm  
  • tinea capitis

Fungal infections also include yeast-like fungi (such as Candida). Candida yeast infections include:

  • diaper rash  
  • oral thrush  
  • cutaneous candidiasis  
  • some cases of genital rashes

Fungal nail infections are most often seen in adults. They often follow fungal infection of the feet. Fungal nail infections may be difficult to treat and may recur often. Toenails are affected more often than fingernails.

People who frequent public swimming pools, gyms, or shower rooms; and people who perspire a great deal commonly have mold-like infections because the fungi that cause them thrive in warm, moist areas.

The risk of getting a fungal infection is increased by closed-in footwear, prolonged moist skin, and minor skin or nail injuries.


  • Nail changes on one or more nails (usually toenails):       o Brittle       o Discolored       o Loss of luster and shine       o Thickening       o Distorted nail shape       o Crumbling of the nail       o Debris under the nail       o Loose (detached) nail

Signs and tests

Your doctor will suspect a fungal infection based on the appearance of the nails.

The diagnosis can be confirmed by scraping the nail for a culture or examining it under a microscope to identify the type of fungus.


Creams and ointments are generally no help in treating onychomycosis. Recently, however, a nail lacquer (called Penlac) has been marketed and may be helpful in some patients.

Oral medications - such as Sporanox (itraconazole) or Lamisil (terbinafine) - may be taken for several months. While these medicines may clear the fungus in about half of all patients, they can cause numerous side effects. Many people are not able to take these medications because of other medications that they are taking, or other medical problems.

Nails grow slowly, so even if treatment is successful, a new, clearer nail may take up to one year to replace the old nail.

Expectations (prognosis)
Fungal nail infections may be difficult to treat and may become a reservoir for fungal organisms, causing them to return in the skin or nails. The fungal nail infection is cured by the growth of new, non-infected nails. Even with successful treatment, a relapse is common.


  • Permanent damage to the nails  
  • Secondary skin infections, including paronychia  
  • Recurrent fungal infections of the nails or other parts of the body

Calling your health care provider
Call your health care provider if you experience persistent fungal nail infections, or if the fingers become painful, red, or drain pus.

Good general health and hygiene help to prevent fungal infections. Keep the skin clean and dry. Take proper care of the nails (see treatment). Wash and dry the hands thoroughly after contact with any fungal infection.

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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