What Is It?

Toenail fungus, also called onychomycosis, is a relatively common condition that disfigures and sometimes destroys the nail. This problem can be caused by several different types of fungi (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, the tough protein that makes up the hard surface of the toenails.

Toenail fungus affects 2% to 18% of all people worldwide and 3% to 5% of people in the United States. It is relatively rare in children, affecting only about 1 out of every 200 people younger than 18. However, the likelihood of getting toenail fungus increases with age. Up to 48% of people have at least one affected toe by the time they reach age 70. Although 2.5 million Americans see a podiatrist annually for treatment of toenail fungus, many more are infected but never seek help. Some people consider toenail fungus just a cosmetic problem and don't bother seeking treatment.

Almost anyone who wears tight-fitting shoes or tight hosiery is more likely to develop toenail fungus, especially if they also practice poor foot hygiene. Another risk is wearing layers of toenail polish, which doesn't allow the nail to breathe. Also, because toenail fungi may spread from foot to foot on the floors of showers and locker rooms, fungal infections of the toenails are especially common among military personnel, athletes and miners. The condition also tends to affect people with chronic illnesses, such as diabetes or HIV, as well as people with circulatory problems that decrease blood flow to the toes. However, many people have no clear risk factors.

Of all the toenails, those 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 the mild trauma of friction from the sides of shoes.


When a toenail develops a fungal infection, it typically turns yellow or brown and becomes thick and overgrown. Foul-smelling debris also may accumulate under the nail, especially at the sides and tip. As the infection continues, the nail either may crumble gradually and fall off or become so thick that the affected toe feels uncomfortable or painful inside shoes.

In a less common variety of toenail fungus, called white superficial onychomycosis, the nail turns white rather than yellow or brown, and the surface becomes soft, dry and powdery.


After you describe your foot symptoms, your doctor will ask you about any factors that may increase your risk of toenail fungus. These include a high-risk occupation, sports participation, tight-fitting shoes or hosiery, poor foot hygiene or the use of heavy toenail polish. Your doctor will ask whether you have a history of poor circulation, diabetes, or any other illness that may decrease your resistance to infection or interfere with blood flow to your toes.

Because psoriasis sometimes can cause nail problems that look similar to a fungal infection, your doctor may ask whether you or anyone in your family has psoriasis. In some people with psoriasis, the nails are the only part of the body affected. The skin is largely spared. Also, it is possible for psoriasis and a fungal infection to affect the same toenail.

If you and your doctor decide that your nail problem is important, the doctor will examine your affected toenail or toenails. To confirm that you have a fungal infection, your doctor will take small samples of the affected nails for examination under a microscope to check for fungi and other microorganisms.

Expected Duration

Toenail fungus rarely heals on its own. It is usually a chronic (long-lasting) condition that can gradually worsen to involve more and more of the nail. Even if the affected nail comes off, the new nail that grows 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, or dissolving it away with a paste that contains urea.

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 solution (Formula 3).

If the infection is in a wider area of your nail, or several nails, your doctor may prescribe an oral antifungal medication, such as Lamisil.   

In very severe cases, when toenail fungus is resistant to treatment, it may be necessary to remove the nail surgically.

Newer treatments that our doctors might discuss with you include laser treatment, which is painless.