Athlete's foot - (tinea pedis)
Athlete's foot (tinea pedis) is a common persistent infection of the foot caused by a microscopic fungus that lives on dead tissue of the hair, toenails, and outer skin layers (dermatophyte). These fungi thrive in warm, moist environments such as shoes, stockings, and the floors of public showers, locker rooms, and swimming pools.
Athlete's foot is transmitted through contact with a cut or abrasion on the bottom (plantar surface) of the foot. In rare cases, the fungus is transmitted from infected animals to humans.
Athlete's foot is a common fungal infection in developed countries, affecting many people at some time in their lives. The condition easily spreads in public places such as communal showers, locker rooms and fitness centers.
Usually the condition affects the spaces between your toes, but it can spread to your toenails and the soles and sides of your feet. The infection can also involve your palms, groin or underarms. Although it occurs primarily in adults, athlete's foot can also affect children.
Also called tinea pedis, athlete's foot is closely related to other skin conditions with similar names. Tinea is a type of fungus, and pedis is the Latin word for "foot." Other names for athlete's foot are ringworm of the foot, and dermatophytosis, derived from the Greek words for "skin" and "plant."
Other common tinea infections include:
Changing socks, keeping your feet dry and alternating shoes can help you prevent athlete's foot. Often, athlete's foot responds well to treatments you apply to your skin. More severe cases may require oral medications.
Signs and symptoms
The signs and symptoms of athlete's foot can be numerous, but you probably won't have all of them:
People of ancient times believed that athlete's foot was caused by insect bites. In the 19th century, scientists discovered microorganisms, and later a group of fungi called dermatophytes proved to be the primary culprit. The dermatophyte most often implicated in athlete's foot is Trichophyton rubrum. The next most common is Trichophyton mentagrophytes, followed by Epidermophyton floccosum.
These organisms sprout tendril-like extensions that infect the superficial layer of the skin. In response to this fungal growth, the basal layer of the skin produces more skin cells than usual. As these cells push to the surface, the skin becomes thick and scaly. Most often, the more the fungi spread, the more scales your skin produces.
The organisms that cause athlete's foot thrive in damp, close environments created by thick, tight shoes that can pinch the toes together and create warm, moist areas in between. Damp socks increase the risk. The infection isn't found as often in areas of the world where shoes aren't worn. Warm, humid settings that promote heavy sweating favor its spread.
The fungus is carried on fragments of skin or other particles that contaminate floors, mats, rugs, bed linens, clothes, shoes and other surfaces. Plastic shoes in particular provide a welcoming environment for fungal growth and infection. Person-to-person contact is another means of transmission. Although transmission can occur within a household, the infection is more commonly passed along in public areas — locker rooms, saunas, swimming pools, communal baths and showers. Not everyone who carries the fungus develops signs and symptoms of athlete's foot.
Those who are vulnerable include people with weakened immune systems, for example people with diabetes or HIV/AIDS. People with atopic dermatitis, a chronic, inherited skin disease characterized by itchy, inflamed skin, also are more susceptible than others are. Fungal infections of the foot become more common with age. There also may be a genetic predisposition for athlete's foot.
When to seek medical advice
If you notice a foot rash that doesn't improve within 2 weeks with self-care steps, then see your doctor. See someone sooner if you notice excessive redness, swelling, drainage or fever.
Screening and diagnosis
Your doctor will want to determine if your symptoms are caused by athlete's foot or by another skin disorder, such as dermatitis or psoriasis.
You probably will be asked about exposure to contaminated areas or contacts with people who have athlete's foot.
Your doctor may take skin scrapings or fluid samples from your foot to view them under a microscope to identify a fungus within minutes. If the sample shows fungus, an antifungal medication is the usual treatment. If the test is negative but your doctor still suspects that you have athlete's foot, a sample may be sent to a laboratory to determine whether it will grow fungus under the right conditions. This test is known as a culture, and it may take weeks to get results. Your doctor may also order a culture if your condition doesn't respond to treatment.
The fungal infection can create an environment that invites a secondary bacterial infection. By producing an antibiotic substance, the fungus can kill off vulnerable bacteria and favor the overgrowth of hardier, resistant types. In turn, the bacteria release substances that can cause tissue breakdown — soggy skin and painful eroded areas between the toes.
After an episode of athlete's foot, proteins might enter your bloodstream, leading to an allergic reaction that may cause an eruption of blisters on your fingers, toes or hands (dermatophytid reaction).
For mild conditions, your doctor may advise you to apply a prescription or over-the-counter antifungal ointment, lotion, powder or spray. Most infections respond well to these topical agents, which include:
If your fungal infection is severe or doesn't respond to topical medicine, your doctor may give you a prescription oral medication. Oral medications include:
Side effects from these oral medications include gastrointestinal upset, rash and abnormal liver function tests.
According to the Food and Drug Administration (FDA), oral Sporanox and oral Lamisil may be linked to rare cases of liver failure and death. Oral Sporanox may weaken the heart's contractions and shouldn't be prescribed for people with a history of heart failure.
Griseofulvin (Grisactin), an older oral medication, has been prescribed less often since the introduction of the newer medicines. It is effective, but can take months to clear up the infection. Its most common side effect is headache, and it occasionally causes discomfort in the digestive tract, sensitivity to light, rashes or a drop in your white blood cell count.
Your doctor may prescribe an oral antibiotic if you have an accompanying bacterial infection. In addition, your doctor may recommend wet dressings, steroid ointments and an oral corticosteroid medication, such as prednisone, to treat blisters on other areas of your body caused by allergic reactions. Compresses or vinegar soaks may help clear up blisters or soggy skin.
These tips can help you avoid athlete's foot or ease the symptoms if infection occurs: