Ringworm is a skin infection caused by a fungus. Ringworm can affect skin on your body (tinea corporis), scalp (tinea capitis), groin area (tinea cruris, also called jock itch), or feet (tinea pedis, also called athlete's foot).

Often, there are several patches of ringworm on your skin at once.

Ringworm is a common skin disorder, especially among children, but it may affect people of all ages. Although its name suggests otherwise, it is caused by a fungus, not a worm.

Many bacteria and fungi live on your body. Some of these are useful to you and your body. Others can multiply rapidly and form infections. Ringworm occurs when a particular type of fungus grows and multiplies anywhere on your skin, scalp, or nails.

Ringworm is contagious. It can be passed from one person to the next by direct skin-to-skin contact or by contact with contaminated items such as combs, unwashed clothing, and shower or pool surfaces. You can also catch ringworm from pets that carry the fungus. Cats are common carriers.

The fungi that cause ringworm thrive in warm, moist areas. Ringworm is more likely when you have frequent wetness (such as from sweating) and minor injuries to your skin, scalp, or nails.

The symptoms of ringworm include:

• Itchy, red, raised, scaly patches that may blister and ooze. The patches often have sharply-defined edges. They are often redder around the outside with normal skin tone in the center. This may create the appearance of a ring. Your skin may also appear unusually dark or light.
• When your scalp or beard is infected, you will have bald patches.
• If nails are infected, they become discolored, thick, and even crumble.

Your doctor will diagnose ringworm primarily based on the appearance of the skin. If tests are needed, the fungus may appear florescent when your skin is examined with a blue light (called a Wood's lamp) in a dark room. A more definitive diagnosis can be made by scraping the affected area of skin and examining the cells under a microscope.

Ringworm usually responds well to self-care within 4 weeks without having to see a doctor.

• Keep your skin clean and dry.
• Apply over-the-counter antifungal or drying powders, lotions, or creams. Those that contain miconazole, clotrimazole, or similar ingredients are often effective.
• Wash sheets and nightclothes every day while infected.

A severe or persistent infection may require treatment by a doctor. Antifungal pills may be given and are necessary if your hair is infected. Prescription antifungal skin medications, such as ketoconazole, are stronger than over-the-counter products and may be needed. Antibiotics may also be needed to treat related bacterial infections.

Infected pets also should be treated.

Skin medication is usually successful at treating Ringworm within 4 weeks. If your ringworm infection is severe or resistant (meaning that it does not respond well to self-care), it will usually respond quickly to antifungal pills.

• Spread of ringworm to other areas
• Bacterial skin infections
• Contact dermatitis or other skin disorders
• Side effects from medications

Call your doctor right away if you have any signs of a bacterial infection, which can result from scratching. These signs include swelling, warmth to the touch, sudden worsening in redness of the patches, red streaking, pus, discharge, and fever.

Call your doctor if:

• Ringworm infects your scalp or beard.
• Your skin does not improve after 4 weeks of self-care.

To prevent ringworm:

• Keep your skin and feet clean and dry.
• Shampoo regularly, especially after haircuts.
• Do not share clothing, towels, hairbrushes, combs, headgear, or other personal care items. Such items should be thoroughly cleaned and dried after use.
• Wear sandals or shoes at gyms, lockers, and pools.
• Avoid touching pets with bald spots.

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Gupta AK. Treatments of tinea pedis. Dermatol Clin. 2003; 21(3): 431-462.

Pratte M. Common skin conditions in athletes. Clin Fam Pract. 2003; 5(3): 653.