Athlete's foot

Definition

Athlete's foot is an infection of the feet caused by fungus. The medical term is tinea pedis. Athlete's foot may last for a short or long time and may come back after treatment.

Alternative Names

Tinea pedis; Fungal infection - feet; Tinea of the foot; Infection - fungal - feet; Ringworm - foot

Causes, incidence, and risk factors

The body normally hosts a variety of microorganisms, including bacteria and fungi. Some of these are useful to the body. Others may, under certain conditions, multiply rapidly and cause infections. Athlete's foot occurs when a particular type of fungus grows and multiplies in your feet (especially between your toes) or, less commonly, your hands.

Of the fungal infections known as tinea infections, Athlete's foot is the most common. It may occur at the same time as other fungal skin infections such as ringworm or jock itch. These fungi thrive in warm, moist areas. Your risk for getting athlete's foot increases if you:

• Wear closed shoes, especially if they are plastic-lined
• Keep your feet wet for prolonged periods of time
• Sweat a lot
• Develop a minor skin or nail injury

Athlete's foot is contagious, and can be passed through direct contact, or contact with items such as shoes, stockings, and shower or pool surfaces.

Symptoms

The most common symptom is cracked, flaking, peeling skin between the toes. The affected area is usually red and itchy. You may feel burning or stinging, and there may be blisters, oozing, or crusting. In addition to the toes, the symptoms can also occur on the heels, palms, and between the fingers.

If the fungus spreads to your nails, they can become discolored, thick, and even crumble.

See also: Fungal nail infection

Signs and tests

The diagnosis is based primarily on the appearance of your skin. If tests are performed, they may include:

• Skin culture (fungi from flecks of skin are able to grow in the lab)
• Skin lesion biopsy (examination may show fungus under the microscope)
• Skin lesion KOH exam (skin scrapings in KOH show fungus under the microscope)

Treatment

Over-the-counter antifungal powders or creams can help control the infection. These generally contain miconazole, clotrimazole, or tolnaftate. Continue using the medicine for 1 - 2 weeks after the infection has cleared from your feet to prevent the infection from returning.

In addition:

• Keep your feet clean and dry, especially between your toes.
• Wash your feet thoroughly with soap and water and dry the area very carefully and completely. Try to do this at least twice a day.
• Wear clean, cotton socks and change your socks and shoes as often as necessary to keep your feet dry.

Athlete's foot almost always responds well to self-care, although it may come back. To prevent future infections, follow the steps listed in Prevention.

Severe, ongoing infections that don't respond to 2 - 4 weeks of self-care, and frequently recurring athlete's foot, may require further treatment by your health care provider. Stronger, prescription antifungal medications may be needed. These include topical medicines, like ketoconazole or terbinafine, and pills. Antibiotics may be necessary to treat secondary bacterial infections that occur in addition to the fungus (for example, from scratching).

Expectations (prognosis)

Athlete's foot infections range from mild to severe and may last a short or long time. They may persist or recur, but they generally respond well to treatment. Long-term medication and preventive measures may be needed.

Complications

• Recurrence of athlete's foot
• Secondary bacterial skin infections such as cellulitis
• Lymphangitis, lymphadenitis
• Systemic side effects of medications (see the specific medication)

Calling your health care provider

Call your doctor right away if:

• Your foot is swollen and warm to the touch, especially if there are red streaks. These are signs of a possible bacterial infection. Other signs include pus or other discharge and fever.
• You have diabetes and develop athlete's foot.

Also call your doctor if athlete's foot symptoms do not go away within one month of using self-care measures.

Prevention

To prevent athlete's foot, follow these measures:

• Dry your feet thoroughly after bathing or swimming.
• Wear sandals or flip-flops at a public shower or pool.
• Change your socks often to keep your feet dry. This should be done at least once a day.
• Use antifungal or drying powders to prevent athlete's foot if you are susceptible to getting it, or you frequent areas where athlete's foot fungus is common (like public showers).
• Wear shoes that are well ventilated and, preferably, made of natural material such as leather. It may help to alternate shoes each day, so they can dry completely between wearings. Avoid plastic-lined shoes.

References

Habif, TP. Clinical Dermatology. 4th ed. St. Louis: Mosby; 2004.

Long SS, Pickering LK, Prober CG, eds. Principles and Practice of Pediatric Infectious Diseases. 2nd ed. New York, NY: Elsevier, 2003.