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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Onychomycosis is caused by a fungus. The fungi that cause onychomycosis survive in warm, moist environments. It is spread through direct contact with the fungus.
Anyone can get fungal nail infections. Factors that increase your chance of onychomycosis include:
Onychomycosis can affect one or more nails. It most commonly occurs on toenails.
Onychomycosis may cause:
Your doctor will ask about your symptoms and medical history. A physical exam will be done. 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. Results make take several weeks.
Tests on the nail sample may include:
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:
Antifungal medications are used to treat onychomycosis. Medications may be oral or topical.
Surgery to remove the nail is sometimes done in severe cases. A new nail grows in its place unless the nail matrix that makes the nail is destroyed.
To help reduce your chance of onychomycosis:
American Academy of Dermatology
American Board of Dermatology
The College of Family Physicians of Canada
Garcia-Doval I, Cabo F, et al. Clinical diagnosis of toenail onychomycosis is possible in some patients: cross-sectional diagnostic study and development of a diagnostic rule. Br J Dermatol. 2010;163(4):743-751.
Nandedkar-Thomas MA, Scher RK. An update on disorders of the nails. J Am Acad Dermatol. 2005;52:877-887.
Onychomycosis. EBSCO DynaMed website. Available at:
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Updated July 27, 2012. Accessed December 3, 2012.
Rodgers P, Bassler M. Treating onychomycosis. Am Fam Physician. 2001;63:663-672,677-678.
Thomas J, Jacobson GA, et al. Review article. Toenail onychomycosis: an important global disease burden. J Clin Pharm Ther. 2010;35(5):497-519.
Last reviewed October 2014 by David L Horn, MD, FACP
Last Updated: 1/13/2014