Home > Foot Problems > Toenails
Toenail Fungus (Onychomycosis)
| * Explanation | * Symptoms | * Diagnosis | * Duration |
| * Prevention | * Treatment | * Call your Doctor | * Prognosis |
A fungal infection of the toenail, also called onychomycosis, is a relatively common condition that disfigures and sometimes destroys the nail. Onychomycosis 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, they feed on keratin, the tough, horny protein that makes up the hard surface of the toenails. In about 78 percent of cases, the infecting toenail fungus belongs to a group of fungi called dermatophytes, which include Trichophyton rubrum and Trichophyton interdigitale. Another 14 percent of fungal infections are caused by yeasts, 5 percent by molds and 3 percent by mixed infections (usually combinations of bacteria and fungi).
Toenail fungus is a very common condition that affects 2 percent to 18 percent of all people worldwide and 3 percent to 5 percent of Australians. It is relatively rare in children, affecting only about one out of every 200 people younger than 18. However, its incidence increases with age, so that up to 48 percent of all individuals have at least one affected toe by the time they reach age 70. Although a half million Australians see a podiatrist annually for treatment of toenail fungus, an estimated 1 million more are infected but never seek help. For some people, toenail fungus is a cosmetically embarrassing problem that they cover up by wearing closed-toe shoes or layers of toenail polish.
Almost anyone who wears tight-fitting shoes or tight hosiery has an increased risk of developing toenail fungus, especially if they also practice poor foot hygiene. Wearing occlusive layers of toenail polish, which doesn't allow the nail to breathe, is another risk factor. 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 persons with chronic illnesses, such as diabetes or HIV, as well as individuals with circulatory problems that decrease blood flow to the toes. However, many people have no clear predisposing 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 in part due to the fact that 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 may also accumulate under the nail, especially at the sides and tip. As the infection becomes longstanding, the nail may either gradually crumble 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.
What Your Doctor Looks For
After you describe your foot symptoms, your doctor will ask you about any risk factors that might increase your risk of toenail fungus. These include a high-risk occupation, sports participation, tight-fitting shoes or hosiery, poor foot hygiene or use of heavy toenail polish. Your doctor will also ask whether you have a history of poor circulation, diabetes, HIV or any other illness that might decrease your resistance to infection or interfere with blood flow to your toes.
Because psoriasis can sometimes cause nail problems that look similar to a fungal infection, your doctor may ask whether you or anyone in your family suffers from psoriasis. In some patients 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 exist simultaneously in the same toenail.
Before proceeding, your doctor will ask whether you are interested in treatment. There is often no concern medically and, therefore, toenail fungus may be a cosmetic concern only.
After reviewing your symptoms, risk factors and medical history and after you and your doctor decide that this nail problem is important, he or she will examine your affected toenail or toenails. To confirm that you actually 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 the microscope and cultured (checked for growth of fungi and other microorganisms).
Toenail fungus is optimally diagnosed in the laboratory, rather than by the physical appearance of the affected toenail. If the toenail really does have a fungal infection, long-term treatment can be considered, and it should not be started based on an incorrect diagnosis.
Toenail fungus rarely heals on its own. It is usually a chronic condition that gradually progresses to involve more and more of the nail. Even if the affected nail falls off spontaneously or is knocked off, the nail that regrows is usually infected with fungus.
You can help to prevent toenail fungus by:
There are several approaches to therapy. Treatment may begin with your doctor removing a 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.
Next, if the infection is mild and very localized, 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 involves 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 persons taking terfenadine, astemizole, cisapride , midazolam, triazolam or lovastatin.
Fluconazole, another oral antifungal medication, is also effective against toenail fungus, but the Food and Drug Administration (FDA) has not yet approved fluconazole as a treatment for this disorder.
In very severe cases of toenail fungus resistant to therapy, surgical removal of the nail may be necessary.
You may wish 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.
According to one study involving 195 patients with toenail fungus, 81 percent of those treated with terbinafine and 63 percent of those treated with itraconazole were cured of their fungus after 12 weeks of therapy. However, even after the fungus was dead in these patients, only 36 percent to 50 percent had completely clear, normal-looking nails.
After treatment with itraconazole, 9 percent to 11 percent of patients relapse, and their toenail fungus returns after nine to 12 months. After treatment with terbinafine, about 12 percent of patients relapse within 12 months.