Ringworm is a fairly common fungal infection that can affect several different areas of the body. It is caused by species of fungi called dermatophytes that live on the dead tissues of skin, hair and nails. Some species live preferentially on humans, others on animals.

When people use the term ringworm, they often are referring to the infection that causes a ring-shaped rash and bald spot on the skin (tinea corporis) or scalp (tinea capitis). However, ringworm also can affect the feet (tinea pedis) or the groin (tinea cruris) and other areas of the body.

Normally, a person’s skin cells move from the lowest layer of the skin to the highest layer of the skin over the course of about a month. Once the skin cells reach the outermost layer, they die and scale off in flakes.

The fungus that causes ringworm grows in moist, warm environments. It lives on the outermost layer of the skin, hair and nails and feeds on the cells there. As it multiplies on the skin, it spreads out in a circle, leaving its distinctive ring-like pattern. Despite its name, there is no worm present under the skin in patients with this infection.

Ringworm is contagious, and people may become infected with the fungus from many different sources. Direct contact with an infected person can transmit the fungus. Direct contact with an infected animal’s skin or hair also can cause a person to become infected with ringworm. Animals with ringworm often have a patch of skin where hair is missing. Animals known to transmit ringworm include:

• Cats (especially kittens)
• Dogs (especially puppies)
• Horses
• Ferrets
• Rabbits
• Guinea pigs
• Cows
• Goats
• Pigs

Direct contact with contaminated, damp surfaces (e.g., public showers, locker room floors) and other contaminated items (e.g., combs, unwashed clothing) also can result in ringworm infection. In rare cases, a person can become infected with ringworm after coming into contact with infected soil.

People infected with ringworm are at risk for several complications. Ringworm may spread from the source of origin to other areas of the body. Ringworm is also associated with bacterial skin infections (from scratching the skin with dirty nails) and certain types of skin rashes (e.g., contact dermatitis). Symptoms of these conditions are similar to those of ringworm, except that bacterial skin infections may also include fever.