(Tinea Unguium; Fungal Nail Infection)

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


Onychomycosis is an infection of the toenail or fingernails.

Fungal Infection of the Toenails

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The infection is caused by a fungus. It can spread to humans from direct contact. This type of fungus lives in warm, moist places such as showers.

Risk Factors

Things that increase the risk of onychomycosis include:


Onychomycosis may cause:

  • Thickened nail that is difficult to cut
  • Brittle or ragged nail
  • Discolored or unsightly nail
  • Pain in the nail with normal use

It may happen in one or more of the nails.


The doctor will ask about and past health. A physical exam will be done. A piece of the nail may be removed for testing. Results make take several weeks.


Onychomycosis can be hard to treat. It may return after treatment. Treatment options include:

  • Antifungal medicine—may be pills or creams and lotions applied to the area
  • Surgery—nail may need to be removed for severe infections

Nails grow slowly. It can take up to a year to clear the nail.


Steps that may lower the chance of onychomycosis:

  • Keep feet clean. Dry them completely after washing.
  • Keep hands dry. Wear rubber gloves when cleaning.
  • Keep nails short and clean. Trim them straight across.
  • Do not trim or pick at the skin near nails.
  • Do not wear shoes that are too tight.
  • Wear cotton socks that can pull moisture away from skin. Change socks if they are damp.
  • Use footwear when walking around swimming pools, locker rooms, and other public places.
  • Avoid artificial nails. They can trap moisture.


American Academy of Dermatology
Foot Health Facts—American College of Foot and Ankle Surgeons


Canadian Podiatric Medical Association
The College of Family Physicians of Canada


Nandedkar-Thomas MA, Scher RK. An update on disorders of the nails. J Am Acad Dermatol. 2005;52(5):877-887.
Onychomycosis. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T115521/Onychomycosis . Updated December 3, 2018. Accessed January 11, 2019.
Onychomycosis. Merck Profesional Manual. Available at: https://www.merckmanuals.com/professional/dermatologic-disorders/nail-disorders/onychomycosis. Updated November 2017. January 11, 2019.
Westerberg DP, Voyack MJ. Oonychomycosis: Current trends in diagnosis and treatment. Am Fam Physician. 2013;88(11):762-770.
Last reviewed November 2019 by EBSCO Medical Review Board Monica Zangwill, MD, MPH
Last Updated: 11/5/2019

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