Newswise — A thick, crumbling yellow toenail is probably not high on the list of health concerns, but it might be nice if it looked better.

Most often, the cause for a thick nail is a fungal infection, according to the October issue of Mayo Clinic Health Letter. The infection can continue indefinitely if not treated. Even with treatment, nail fungus can be difficult to clear up.

Fungal organisms find their way into the skin through thin breaks or even a small separation between a nail and the nail's bed. Fungi don't need sunlight to survive and do very well in warm, moist environments. For example, warm toes encased in a dark shoe are an ideal setup.

The infection is more common in older adults, in part because of decreased resistance to infection due to diabetes, circulation problems or a weakened immune system. Other risk factors include working in a humid environment, wearing shoes that don't "breathe" and socks that don't absorb perspiration, and walking barefoot in damp public places such as gyms and swimming pools.

The first sign of fungal nail infection -- the medical term is onychomycosis (on-i-ko-mi-KO-sis) -- may be a yellow or white spot under the nail's tip. Over time, the nail may thicken, become crumbly or ragged or may start to separate from the nail bed.

If a nail isn't painful or too bothersome, some people opt not to treat the fungal infection, instead watching for troublesome changes and carefully filing the affected nail to keep it trimmed and thinned. Treatment options include:

Self-care: Any nonprescription antifungal cream applied to the nail's surface could improve a superficial infection. Other topical treatment options are Vicks VapoRub, tea tree oil or white vinegar; however, no rigorous studies have shown that these approaches work.

Antifungal oral medications: Two commonly prescribed medications are itraconazole (Sporanox) and terbinafine (Lamisil). Fluconazole (Diflucan) is another option. Typically, these medications are used for six to 12 weeks. Results aren't evident until complete nail regrowth, which can take about a year. Treatment success rate is 40 to 90 percent. For people over age 60, success rates are 60 to 64 percent. Among those successfully treated, 15 to 20 percent will have a recurrence.

These medications can have serious side effects. They include heart failure, liver damage, liver failure and possible adverse interaction with other drugs, including some blood thinners and certain cholesterol-lowering drugs.

Antifungal nail lacquer: Ciclopirox (Penlac) may help if the infection is superficial and does not affect the nail bed. Treatment involves coating the nail daily for a year. The cure rate is about 10 percent.

Mayo Clinic Health Letter is an eight-page monthly newsletter of reliable, accurate and practical information on today's health and medical news. To subscribe, please call 800-333-9037 (toll-free), extension 9771, or visit http://www.HealthLetter.MayoClinic.com.

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