(Tinea Unguium; Fungal Nail Infection)

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


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

Fungal Infection of the Toenails

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The infection is caused by a fungus. The type that causes onychomycosis live in warm, moist environments. The fungus spreads to humans after direct contact.

Risk Factors

Anyone can get fungal nail infections. Factors that increase your chances of onychomycosis include:


Onychomycosis can affect one or more nails. It is more common on toenails.

Onychomycosis may cause:

  • Thickened nail that is difficult to cut
  • Brittle or ragged nail
  • Discolored or unsightly nail
  • Pain in the nail when doing ordinary activities


Your doctor will ask about your symptoms and past health. A physical exam will be done. The doctor may scrape or clip the nail. A sample will be sent for testing. Results make take several weeks.


Onychomycosis can be difficult to treat. It may return after treatment. Nails also grow slowly. It can take up to a year for treatment to completely clear the nail. Talk with your doctor about the best treatment plan for you. Treatment options include:

  • Antifungal medicine—may be in pill form or creams and lotions
  • Surgery—nail may need to be removed with severe infections


To help reduce your chances of onychomycosis:

  • Keep your feet clean. Dry them completely after washing.
  • Keep your hands dry and wear rubber gloves when cleaning.
  • Keep nails short and clean. Trim them straight across.
  • Do not trim or pick at the skin near your nails.
  • Avoid injuring your toenails.
  • Avoid shoes that are too tight.
  • Wear absorbent cotton socks. Change them if they become damp.
  • Avoid walking barefoot around swimming pools, locker rooms, and other public places.
  • Avoid artificial nails. They can trap moisture.
  • If you have diabetes, see your doctor about steps you can take to control your blood sugar.


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 Manula. 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 January 2019 by EBSCO Medical Review Board Monica Zangwill, MD, MPH
Last Updated: 1/8/2019

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