Toenail Fungus (Onychomycosis)
Medically reviewed on May 15, 2018
What Is It?
Toenail fungus is a condition that disfigures and sometimes destroys the nail. It is also called onychomycosis
Toenail fungus can be caused by several different types of fungi. Fungi are microscopic organisms related to mold and mildew.
These fungi thrive in the dark, moist and stuffy environment inside shoes. As they grow, fungi feed on keratin. Keratin is the protein that makes up the hard surface of the toenails.
Factors that increase the risk of developing toenail fungus include:
Wearing tight-fitting shoes or tight hosiery
Practicing poor foot hygiene
Wearing layers of toenail polish, which doesn't allow the nail to breathe
Being a military personnel, athlete or miner. This is because toenail fungi may spread from foot to foot on the floors of showers and locker rooms.
Having a chronic illnesses, such as diabetes or HIV
Having a circulatory problem that decreases blood flow to the toes
However, many people with toenail fungus have no clear risk factors.
Toenails on the big toe and little toe are the most likely to develop a toenail fungus. This may be partly because the big toe and little toe are constantly exposed to friction from the sides of shoes.
When a toenail develops a fungal infection, it typically turns yellow or brown. It becomes thick and overgrown. Foul-smelling debris also may accumulate under the nail.
As the infection continues, the nail may crumble gradually and fall off. Or, it may become so thick that the affected toe feels uncomfortable or painful inside shoes.
A less common variety of toenail fungus is called white superficial onychomycosis. The nail turns white rather than yellow or brown. The surface becomes soft, dry and powdery.
You will describe your foot symptoms to your doctor. He or she will ask about any factors that may increase your risk of toenail fungus. These include:
A high-risk occupation
Tight-fitting shoes or hosiery
Poor foot hygiene
Use of heavy toenail polish
A history of illness that may decrease your resistance to infection or interfere with blood flow to your toes. These include:
A skin disease called psoriasis sometimes can cause nail problems that look similar to a fungal infection. As a result, your doctor may ask whether you or a family member has psoriasis. It is possible for psoriasis and a fungal infection to affect the same toenail.
Your doctor will examine your affected toenail or toenails. Often the diagnosis can be made based on the appearance of toenails. Your doctor may take small samples of the affected nails. These samples will be sent to a laboratory where they are tested for fungi and other infectious agents.
Toenail fungus rarely heals on its own. It is usually a chronic (long-lasting) condition. It can gradually worsen to involve more and more of the nail. Even if the affected nail comes off, the new nail may be infected with fungus.
To help to prevent toenail fungus:
Wear comfortable shoes and hosiery that allow your feet some breathing space.
Wear shoes, sandals or flip-flops in community showers or locker rooms.
Wash your feet every day. Dry them thoroughly, and use a good-quality foot powder.
Wear clean socks or stockings every day.
Keep your toenails trimmed.
Disinfect pedicure tools before you use them.
Treatment may begin with your doctor removing as much of the infected nail as possible. This can be done by:
Trimming the nail with clippers
Filing it down
Dissolving it away with a paste that contains urea and bifonazole
If the infection is mild and limited to a small area of your nail, your doctor may prescribe an antifungal cream or a medicated nail polish.
If the infection is in a wider area of your nail, or several nails, your doctor may prescribe an oral antifungal medication. Examples include itraconazole (Sporanox) and terbinafine (Lamisil). Both drugs occasionally cause troublesome side effects. Itraconazole can produce serious drug interactions.
In very severe cases, when toenail fungus is resistant to treatment, it may be necessary to remove the entire nail surgically.
When To Call a Professional
You don't need to call your doctor unless you have pain or difficulty walking. You can show your doctor your toenails at your next office visit or schedule an appointment if you want to discuss treatment with a prescription medication.
Most people treated with an oral antifungal medicine are cured after a few months of therapy. However, even after the fungus is dead, the nail may never become clear and normal-looking.
The fungus returns in some people even after successful treatment with an oral antifungal medication.
Learn more about Toenail Fungus (Onychomycosis)
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Insitutes of Health
1 AMS Circle
Bethesda, MD 20892-3675
American Podiatric Medical Association (APMA)
9312 Old Georgetown Road
Bethesda, MD 20814
American Academy of Podiatric Sports Medicine
American College of Foot & Ankle Orthopedics & Medicine
5272 River Road, Suite 630
Bethesda, MD 20816
American College of Foot and Ankle Surgeons
8725 West Higgins Road
Chicago, IL 60031-2724