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Mycotic Nails - Fungal Nail Infection

Overview, Causes, & Risk Factors

A fungal nail infection is a condition in which a fungus or yeast infects the nails.

What is going on in the body?

A fungal nail infection is usually caused by a fungus called Trichophyton.

What are the causes and risks of the infection?

Fungal skin infections, such as athlete's foot, often lead to fungal nail infections. It is most common in adolescent and adult males and is rare in women and children under age 12. The fungus that causes the infection lives in warm, moist environments such as showers and locker rooms. A person is more likely to develop a fungal infection if he or she:

  • doesn't dry feet well after swimming or bathing
  • has sweaty feet
  • walks barefoot in locker rooms and showers
  • wears tight shoes and socks

  • Symptoms & Signs

    What are the signs and symptoms of the infection?

    Nails infected with a fungus may have the following characteristics:

  • discolored
  • dull, or no longer shiny
  • thickened, with crumbling edges
  • If a toenail becomes thick, it can be painful to wear shoes.

    Diagnosis & Tests

    How is the infection diagnosed?

    Diagnosis of a fungal nail infection begins with a medical history and physical exam. The healthcare provider may cut a small portion of the nail plate. It is sent to a lab so the organism can be identified.

    Prevention & Expectations

    What can be done to prevent the infection?

    It is hard to prevent a fungal nail infection, but here are a few tips:

  • Wear a shower shoe or sandal in public places instead of going barefoot.
  • Use an antifungal powder, such as miconazle, in socks and shoes.
  • Keep socks clean.
  • Wash socks each time with an antifungal solution, such as clotrimazole, if you are susceptible to the fungus.
  • Keep feet clean and dry.
  • Go barefoot at home, whenever possible.
  • Avoid use of nail polish and polish remover.
  • Cut toenails straight but not too short.
  • What are the long-term effects of the infection?

    Fungus can cause the nail plate to come loose from the skin. This enables water or sweat to get under the nail. Bacteria can build up and cause skin breakdown. This can lead to a secondary bacterial infection. The infection can result in cellulitis, which is an infection of the connective tissue under the skin. Rarely, sepsis, or blood poisoning, can occur.

    What are the risks to others?

    Fungus may be transmitted to others who share bathing facilities or footwear.

    Treatment & Monitoring

    What are the treatments for the infection?

    Treatment of a fungal nail infection includes the following:

  • trimming and thinning the nail plate
  • taking an oral antifungal medicine, such as terbinafine
  • removing the nail temporarily and treating the area underneath with an antifungal ointment
  • What are the side effects of the treatments?

    Antifungal ointments may cause an allergic reaction. Oral antifungal medications may cause stomach upset or allergic reaction.

    What happens after treatment for the infection?

    Antifungal medications are expensive and require monitoring by the healthcare provider for the length of treatment. Once the medicine is stopped, it may take several months before the nail plate is cleared of the fungus. The fungus can, and often does, return. Any new or worsening symptoms should be reported to the healthcare provider.


    Author:Bill O'Halloran, DPM
    Date Written:
    Editor:Cafiero, Celeste, MA
    Edit Date:05/19/00
    Reviewer:Janet E. Simon, DPM
    Date Reviewed:09/25/01