Loading icon
Press enter or spacebar to select a desired language.
Health Information Center


  • Amy Scholten, MPH
Publication Type:



(Tinea Unguium; Fungal Nail Infection)


Onychomycosis is an infection of the toenail or fingernails.

Fungal Infection of the Toenails.

si55551611_96472_1http://services.epnet.com/getimage.aspx?imageiid=77327732si55551611.jpgsi55551611.jpgNULLjpgsi55551611.jpgNULL\\hgfiler01a\intellect\images\si55551611.jpgNULL92NULL2008-12-10352540252440Copyright © Nucleus Medical Media, Inc.


The infection is caused by a type of fungus. It can spread to people if they touch it. This type of fungus lives in warm, moist places such as showers. It can start with another fungus skin infection, such as athlete's foot. From there, it can travel to the nail.

Risk Factors

This infection is more common in adults over 60 years old. It is also more common in men and athletes. Things that increase the risk of this include:

  • Tight shoes that trap in moisture and warmth
  • Athlete's foot
  • Nail injury
  • Problems that can affect blood flow, such as Type 1 or type 2 diabetes and peripheral artery disease (PAD)
  • A weak immune system
  • Contact with others who have the infection
  • Smoking
  • Hyperhidrosis--problems with sweating


Onychomycosis may cause:

  • Thickened nail
  • Brittle or ragged nail
  • Discolored nail
  • Pain in the nail with normal use

It may happen in one or more of the nails.


The doctor will ask about symptoms and past health. A physical exam will be done. A piece of the nail may be taken for testing.


The goal of treatment is to clear the fungus. This infection can be hard to treat. It may return after treatment. Treatment options are:

  • Antifungal medicine taken by mouth or applied to the nail
  • Removal of the nail—in severe infections

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


Things that may lower the risk of onychomycosis:

  • Treating athlete's foot
  • Dry, clean feet and hands
  • Short, clean nails
  • Not trimming or picking skin near nails
  • Well-fitting shoes
  • Dry cotton socks
  • Wearing shoes at swimming pools, locker rooms, and other public places
  • Not using artificial nails




  • Onychomycosis. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/onychomycosis. Accessed May 26, 2022.
  • Onychomycosis. Merck Profesional Manual. Available at: https://www.merckmanuals.com/professional/dermatologic-disorders/nail-disorders/onychomycosis. May 26, 2022.
  • Taylor-Frazier, Winifred, Santiago-Delgado, Zuleica M. et al. Onychomycosis: rapid evidence review. American Family Physician. 2021; 104(4): 359-367


  • April Scott, NP
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.