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. In most cases, the fungus belongs to a group of fungi called dermatophytes, which include Trichophyton rubrum and Trichophyton interdigitale. Other, less common causes of onychomycosis include yeasts and molds.
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, HIV 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 and send them to a laboratory. The nail samples will be examined under a microscope and will be checked for fungi and other microorganisms.
Toenail fungus rarely heals on its own. It is usually a chronic (long-lasting) condition that gradually worsens to involve more and more of the nail. Even if the affected nail comes off, the new nail that grows usually is 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 and bifonazole.
If the infection is mild and limited to a small area of your nail, your doctor may prescribe a medicated nail polish containing either amorolfine (Loceryl) or ciclopirox (Loprox). You should apply the nail polish twice a week until your nail is cured.
If the infection is in a wider area of your nail, or several nails, your doctor will prescribe an oral antifungal medication, such as itraconazole (Sporanox) or terbinafine (Lamisil). Either itraconazole or terbinafine can be taken daily for 12 weeks, or a higher dose of itraconazole can be taken for one week per month for three months. Both itraconazole and terbinafine occasionally cause troublesome side effects, and itraconazole has the potential to produce serious drug interactions.
In very severe cases, when toenail fungus is resistant to treatment, it may be necessary to remove the nail surgically.
When To Call A Professional
You may want to make an appointment to see your family doctor or podiatrist if you notice that a portion of your toenail has become abnormally thick or discolored. Call your doctor promptly if any problem involving your feet or toes makes walking painful or difficult.
Most people treated with an oral antifungal medicine are cured after 12 weeks of therapy. However, even after the fungus is dead, the nail may not immediately or ever become clear and normal-looking.
After successful treatment with itraconazole or terbinafine, the fungus returns in approximately 10% to 20% of people.
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Insitutes of Health
1 AMS Circle
Bethesda, MD 20892-3675