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(Tinea Unguium; Fungal Nail Infection)

Pronounced: ahn-ee-ko-my-KO-sis

En Español (Spanish Version)


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


© 2008 Nucleus Medical Art, Inc.


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.


American Academy of Dermatology

Mayo Clinic

National Institutes of Health, MedlinePlus Home Page


BC Health Guide, British Columbia Ministry of Health

Just the Berries for Family Physicians


Habib TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy . 4th ed. Philadelphia, PA: Mosby Inc; 2004.

Haggerty M. Don’t let fungal nail infections get the upper hand. Dermatology Insights . Spring 2001:30.

Medical encyclopedia: fungal nail infection. National Institutes of Health Medline Plus website. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/001330.htm . Accessed July 13, 2005.

Nail fungus. Mayo Clinic website. Available at: http://www.mayoclinic.com/printinvoker.cfm?objectid=74D7D49E-8563-4EA5-B3DC570459BE33E9 . Accessed July 13, 2005.

Nandedkar-Thomas MA, Scher RK. An update on disorders of the nails. J Am Acad Dermatol . 2005;52:877-887.

Rodgers P, Bassler M. Treating onychomycosis. Am Fam Physician . 2001; 63:663-72,677-8.

Last reviewed January 2008 by David L. Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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