Tinea is a fungus that can grow on your skin, hair or nails. As it grows, it spreads out in a circle, leaving normal-looking skin in the middle. This makes it look like a ring. At the edge of the ring, the skin is lifted up by the irritation and looks red and scaly. To some people, the infection looks like a worm is under the skin. Because of the way it looks, tinea infection is often called “ringworm.” However, there really isn’t a worm under the skin.

You can get a fungal infection by touching a person who has one. Some kinds of fungi live on damp surfaces, like the floors in public showers or locker rooms. You can easily pick up a fungus there. You can even catch a fungal infection from your pets. Dogs and cats, as well as farm animals, can be infected with a fungus. Often this infection looks like a patch of skin where fur is missing.

Fungal infections are named for the part of the body they infect. Tinea corporis is a fungal infection of the skin on the body. (“Corporis” is the Latin word for body.) If you have this infection, you may see small, red spots that grow into large rings almost anywhere on your arms, legs or chest.

Tinea pedis is usually called “athlete’s foot.” (“Pedis” is the Latin word for foot.) The moist skin between your toes is a perfect place for a fungus to grow. The skin may become itchy and red, with a white, wet surface. The infection may spread to the toenails. (This is called tinea unguium — “unguium” comes from the Latin word for nail.) Here it causes the toenails to become thick and crumbly. It can also spread to your hands and fingernails.

When a fungus grows in the moist, warm area of the groin, the rash is called tinea cruris. (“Cruris” comes from the Latin for leg.) The common name for this infection is “jock itch.” Tinea cruris generally occurs in men, especially if they often wear athletic equipment.

Tinea capitis, which is called “ringworm,” causes itchy, red areas, usually on the head. (“Capitis” comes from the Latin for head.) The hair is destroyed, leaving bald patches. This tinea infection is most common in children.

The best way to know for sure is to ask your doctor. Other skin problems can look just like a fungal infection but have very different treatments. To find out what is causing your rash, your doctor may scrape a small amount of the irritated skin onto a glass slide (or clip off a piece of nail or hair). Then he or she will look at the skin, nail or hair under a microscope. After doing this, your doctor will usually be able to tell if your skin problem is caused by a fungus.

Sometimes a piece of your skin, hair or nail will be sent to a lab to grow the fungus in a test tube. This is another way the lab can tell if your skin problem is caused by a fungus. They can also find out the exact type of fungus. This process takes a while because a fungus grows slowly.

Once your doctor decides that you have a tinea infection, medicine can be used to get rid of it. You may only need to put a special cream on the rash for a few weeks. This is especially true for jock itch.

It can be harder to get rid of fungal infections on other parts of the body. Sometimes you have to take medicine by mouth. This medicine usually has to be taken for a long time, maybe even for months. Irritated skin takes time to heal. New hair or nails will have to grow back.

Some medicines can have unpleasant effects on the rest of your body, especially if you’re also taking other medicines. There are some newer medicines that seem to work better with fewer side effects. You may need to have blood tests to make sure that your body is not having a bad reaction to the medicine.

Skin that is kept clean and dry is your best defense. However, you’re also less likely to get a tinea infection if you do the following things:

A fungus rarely spreads below the surface of the body to cause serious illness. Your body usually prevents this. However, people with weak immune systems, such as people with AIDS, may have a hard time getting well from a fungal infection.

Tinea infections usually don’t leave scars after the fungus is gone. Sometimes, people don’t even know they have a fungal infection and get better without any treatment.