For most people, there's no need to run to the doctor to clear up athlete's foot. But not all over-the-counter treatments are equal, and even the best ones may take time to work.

Athlete's foot is a common fungal infection, tinea pedis, of the skin on the feet. Symptoms include severe itching and redness, as well as cracked or blistered skin. The condition doesn't have serious health consequences, but is annoying and can be stubbornly persistent.

The fungus is most often contracted from damp public environments, such as shower rooms at pools or health clubs. It thrives in the warm and moist environment of footwear, making people with sweaty feet especially susceptible. Going barefoot in dry areas - through airport metal detectors, for example - is much less risky, doctors say.

Of the handful of over-the-counter products that claim to kill the fungus, several doctors recommend Lamisil, which is made by Novartis and costs between $10 to $15 a bottle. Lamisil's active ingredient is a 1% solution of terbinafine hydrochloride, which is fungicidal, meaning it kills fungus, while other products merely inhibit the growth of new spores, doctors say. Lamisil was available only with a prescription until 1999, meaning its fungal fighting agents are newer and stronger than those of older products.

Lotrimin Ultra, made by Schering-Plough, uses a similar compound, butenafide hydrochloride, and is sold for between $15 and $17. It went over-the-counter in 2002.

Don't confuse Lotrimin Ultra with the less expensive - and less effective - Lotrimin AF, which has been available without prescription since 1990. Lotrimin AF and Micatin, made by Pfizer, both use miconazole nitrate 2%, and sell for around $6. Similarly, Tinactin, also made by Schering-Plough, with tolnaftate 1% as an active ingredient, is a well-recognized brand, but probably one of the least effective because others have newer, stronger agents to fight fungus, physicians say.

"About 15 years ago, it was probably considered very effective, but that's no longer so," says Herman Rosenberg, a New York City podiatrist.

Treatments come in so-called power-spray form, though there are powders, liquid sprays and creams. Doctors say the effectiveness varies more by brand than form. They also recommend limiting use of shoes that make your feet sweat, and changing out of damp socks immediately.

Though physicians say Lamisil generally works well, several cautioned that the seven-day regiment advised on the label is usually insufficient. Infected people should use the spray for three to four weeks, even if the symptoms disappear.

If over-the-counter treatments fail, prescription medications may be necessary. Generally, these are somewhat more effective on stubborn fungus than the over-the-counter creams and sprays, yet can cost up to three times as much.

Prescription-level medications include Loprox, manufactured by Aventis, or Spectazole, made by Johnson & Johnson. There's also a prescription-only oral version of Lamisil, which doctors say is more effective than its topical counterpart.

Though not all over-the-counter treatments are equally effective in getting rid of athlete's foot, nearly all can prevent the problem, says Arnold Ross, sports podiatry doctor in Los Angeles. "People should be using powder all the time," says Dr. Ross. "For gym-goers, all the more so."