But television commercials for Lamisil, a toenail cure, now feature yellow fungus monsters yucking it up under the nail of a big toe, and larger-than-life pictures of rotting toenails appear in magazine advertisements for Penlac, another treatment.
For the most part, toenail fungus is repugnant but not medically alarming; doctors say most people who seek treatment for the problem do so out of disgust. Yet for some, especially the elderly or those with diabetes, it may lead to other infections. And even in healthy people, the condition can be painful.
Yet treating the infection takes many weeks and is not always successful. A complete cure, when it is achieved, takes a year, the amount of time required for the infected nail to grow out completely. And the process is expensive. Fungus medications can cost up to several hundred dollars for a single course of treatment, and many health insurers do not cover them.
The medical term for toenail fungus is onychomycosis (on-ee-ko-me-KO-sis). The infection is caused by the same types of fungi that cause athlete's foot, and the two often occur together.
''It starts in the sole of the feet when you're a child and grows from the sole to the nail bed,'' said Dr. Nardo Zaias, director of dermatology at Mount Sinai Medical Center in Miami Beach. ''In teenagers, it goes into the groin and causes jock itch and sometimes to the body, causing ringworm.
''But the toenail is a savings bank,'' Dr. Zaias said. ''The fungus goes into the toenail and stays there for life.''
About 20 percent of people have toenail fungus, researchers have found, and the likelihood of getting it increases with age, rising to about 40 percent by age 70. The fungi themselves are everywhere -- not only in locker rooms, hotel rooms and other public places but also in most people's homes.
Toe fungus tends to run in families, because people inherit a vulnerability to it, Dr. Zaias has found. Onychomycosis can occur under the fingernails, but it is far more common in toes, doctors say, because the feet are more often subject to the dark, warm, moist conditions that fungi favor.
Smoking raises the risk of toenail infection, by restricting circulation to the feet. So does diabetes, which also impairs circulation. Using polish on the nails does not invite or intensify the infection, experts say.
The symptoms of toenail fungus are easy to see -- thickened or brittle nails, often a dull color with spots of white or yellow or, in advanced cases, brown or black. But psoriasis can cause similar symptoms. To be certain, some doctors scrape debris from beneath the nail and examine it under a microscope or culture it to see if fungus grows.
Over-the-counter antifungal creams are safe and help some people with mild infections, said Dr. Lloyd S. Smith, a podiatrist in Newton, Mass. Some treatments contain tea tree oil, an antifungal substance derived from an Australian plant. But in most cases, nonprescription treatments are not powerful enough.
One prescription medication, ciclopirox, a topical treatment marketed by Aventis as Penlac, is painted on like nail polish. Patients are instructed to apply it to infected nails each evening before bed. Once a week, they are to take off the accumulated layers with rubbing alcohol.
But treatment with Penlac takes 48 weeks, and a month's supply costs more than $100. In addition, studies suggest that ciclopirox is effective in combating the infection in less than half of all cases, and results in a total cure in fewer than 10 percent.
Terbinafine, marketed by Novartis as Lamisil, may be the best-known prescription treatment for toenail fungus, thanks to the company's monster-filled commercials. Patients take one 250-milligram tablet a day for 12 weeks. After that, the medicine continues to work for a few months.
Terbinafine helps about 2 out of 3 people who take it, doctors say, but it cures the infection in only 38 percent of cases, according to the package insert. Lamisil costs more than $8 per pill, and a complete course of treatment can cost about $700.
In rare cases, the drug has been linked to liver failure and death, and so the Food and Drug Administration has advised doctors to monitor liver function in patients taking it.
People with liver problems should not take Lamisil. Studies have not been done to determine whether the drug is safe for children and pregnant women. Nursing mothers are also advised to avoid it.
Dr. Zaias has experimented with having patients use terbinafine for only one week out of every three months. This approach allows patients to use less of the drug, and it works in more than 90 percent of cases, according to a small study Dr. Zaias conducted and reported last month in the journal Archives of Dermatology.
Another treatment in pill form is itraconazole, marketed by Janssen as Sporanox. It is typically taken twice a day for one week out of four. This cycle is repeated three or four times. A one-week supply costs about $100. Itraconazole is somewhat less effective than terbinafine. It, too, has been linked in rare cases with liver failure, as well as with congestive heart failure.
In the most difficult and painful cases, doctors remove the toenail to help kill the infection. But given the cost, the risks and the time involved in treatment, experts say it is better to try to avoid infection in the first place -- by treating athlete's foot infections as soon as they arise, for example, and by keeping the toes ventilated and clean.
''I recommend sandals,'' said Dr. Lynn A. Drake, a dermatologist at
Massachusetts General Hospital in Boston. ''But one of the most
effective treatments in the world is to keep your nails well groomed and
short.''