What is nail fungus?

What is nail fungus?

Written by

Lauren Dobischok
5 January, 2023

Medically checked article All HOMED-IQ content is reviewed by medical specialists

Nail fungus is a common infection that can cause nails to thicken, become discoloured, or crumble. While most infections are not serious, they can be annoying and disfigure the nails. Fungal nail infections do not go away on its own and can be difficult to treat. Read on to learn more about what nail fungus looks like, how to prevent it, and how to treat it.

What is nail fungus?

Nail fungus (onychomycosis) is an infection of the fingernails or toenails with a fungal organism. Most fungal nail infections are caused by dermatophytes, a fungi that requires keratin to grow (Cleveland Clinic, 2022). Since nails are made of keratin, dermatophyte nail infections can be difficult to get rid of and spread easily. Dermatophytes can also infect the hair and skin. Nail fungus is more common in toenails than fingernails (Mayo Clinic, 2022). 

What does nail fungus look like?

Nail fungus can change your nail’s appearance in several ways. Your nail may:

  • Change colour, often to white, yellow, or brown
  • Thicken or become misshapen
  • Crumble at the edges
  • Become brittle
  • Lift away from the skin of the nail bed
  • Crack or break
  • Smell unpleasant

Source: Cleveland Clinic, 2022

Causes of nail fungus

Fungal nail infections are caused by infection with microscopic organisms known as fungi. Fungi can spread from skin to skin contact with someone who has a fungal infection, sharing contaminated nail clippers or towels, or from contact with contaminated surfaces, such as a pool deck or locker room (Mayo Clinic, 2022). Fungi thrive in moist, warm environments, which is why fungal infections are common in athletes, people whose hands or feet are wet often, or people who often walk barefoot in hot and humid places.

Is nail fungus contagious?

Yes, nail fungus is quite contagious and can be spread through direct or indirect contact. Nail fungus can spread to others and to your other nails (Cleveland Clinic, 2022). 

Symptoms of nail fungus

The main symptoms of nail fungus are discoloration, thickening, or hardening of the nail (CDC, 2022). The fungus may first appear as a slight discoloration, but over time cause the nail to crumble, break, or lift from the nail bed.

Testing for nail fungus

A nail fungus test involves collecting nail clippings and debris from under the nail and sending the material to the laboratory for analysis (Cleveland Clinic, 2022). Since fungi that infect the nails grow slowly, it can take several weeks for the test results to be ready. The test result shows whether nail fungus is present and what type of fungus is causing the infection. 

Nail fungus treatment

Nail fungus can be difficult to eliminate and may require several months of continuous treatment. The most common treatments are topical medications that can be applied directly to the nail. Topical antifungal treatment is usually a cream or liquid that is applied directly to the nails for up to a year (Mayo Clinic, 2022). These treatments can usually be purchased from the drugstore without a prescription. It is important not to stop treatment even if you see signs of improvement, as the fungus can come back easily. 

Oral antifungal medication is the most effective treatment for nail fungus and can only be used after a positive test for fungus. Medication must be taken every day for several months or longer and requires a prescription (CDC, 2022). In some cases, the toenail is also surgically removed to allow healthy, uninfected nails to grow back.

If your nail does not bother you, treatment is not always necessary. Since nail fungus is so difficult to cure, many people choose to live with it if their nail is not overly affected.

How to prevent nail fungus

There is no way to entirely prevent nail fungus. However, the following tips can help reduce your risk of an infection:

  • Avoid walking barefoot in communal places such as locker rooms, public pools, and public showers
  • Keep your feet dry: dry your feet after showering and do not stay in wet socks or shoes for long periods of time
  • Wear shoes that fit correctly
  • Clean your nail clipper before use
  • Cut nails straight across
  • Avoid cutting nails too short or tearing the nails on purpose
  • Only visit licensed nail salons that sterilize their instruments

Source: Cleveland Clinic, 2022


Fungal Nail Infections | Fungal Diseases | CDC. (n.d.). https://www.cdc.gov/fungal/nail-infections.html

Nail fungus – Symptoms and causes. (2022, August 23). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/nail-fungus/symptoms-causes/syc-20353294

Toenail Fungus (Onychomycosis/Tinea Unguium): Symptoms & Causes. (n.d.). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/11303-toenail-fungus

About the author

Lauren Dobischok

Lauren is a health scientist and science communicator currently living in the Netherlands. Originally from Canada, she completed a Research Master’s in Health Sciences at the Netherlands Institute of Health Sciences at Erasmus University Rotterdam (NIHES) with a specialisation in epidemiology. Prior to her master’s degree, she completed a Bachelor’s degree in Health Sciences at Simon Fraser University. With a background in public health, her goal is to create accurate scientific content that is easy to understand and empowers people to make informed decisions. Within Homed-IQ, Lauren works as a Product Developer and Content Lead, working closely with physicians and scientists on medical devices for Homed-IQ’s new products and written communications.