by Shannon DW
(Tinea Unguium; Fungal Nail Infection)


Onychomycosis is an infection of the toenail or fingernails.

Fungal Infection of the Toenails
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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.

Risk Factors

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

  • Shoes that trap in moisture and warmth
  • Athlete's foot
  • Nail injury
  • Type 1 or type 2 diabetes
  • Blood flow problems, such as 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:

  • 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


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 


Onychomycosis. EBSCO DynaMed website. Available at:  . Accessed February 9, 2022.

Onychomycosis. Merck Profesional Manual. Available at: February 9, 2022.

Taylor-Frazier, Winifred, Santiago-Delgado, Zuleica M. et al. Onychomycosis: Rapid Evidence Review. American Family Physician. 2021; 104(4): 359-367

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