Ringworm

Ringworm (tinea) is a fungal skin infection caused by several different fungi and generally classified by its location on the body.

Despite its name, ringworm infection does not involve worms. The name arose because of the ring-shaped skin patches created by the infection.

Athlete's foot (tinea pedis) is a common fungal infection that usually appears during warm weather. The infection may spread from person to person in communal showers and bathrooms or in other moist areas where infected people walk barefoot. It is usually caused by either Trichophyton or Epidermophyton. These fungi most commonly grow in the warm, moist areas between the toes. The fungus can produce mild scaling with or without redness and itching. The scaling may involve a small area or the entire sole of the foot; sometimes even the toenails are involved. Sometimes scaling is severe, with breakdown and painful cracking (fissuring) of the skin. Fluid-filled blisters can also form. Because the fungus may cause the skin to crack, athlete's foot can lead to bacterial infection (see Section 18, Chapter 211), especially in older people and in people with inadequate blood flow to the feet.

Nail ringworm (tinea unguium, onychomycosis (see Section 5, Chapter 72)) is an infection of the nail most often caused by Trichophyton. The fungus may get into the nail, producing a thickened, lusterless, and deformed nail. Infection is much more common on the toenails than on the fingernails. An infected toenail may separate from the toenail bed, crumble, or flake off.

Jock itch (tinea cruris) is much more common in men than in women and develops most frequently in warm weather. The infection begins in the skinfolds of the genital area and can spread to the upper inner thighs. Usually the scrotum is not involved (unlike in yeast infection). The rash has a scaly, pink border. Jock itch can be quite itchy and may be painful. A susceptible person may have repeated infections.

Scalp ringworm (tinea capitis) is primarily caused by Trichophyton. Scalp ringworm is highly contagious and is common among children (see Section 23, Chapter 267), especially black children. It may produce a pink scaly rash that may be somewhat itchy, or it may produce a patch of hair loss without a rash. Less commonly it can cause a painful, inflamed, swollen patch on the scalp that sometimes oozes pus (a kerion). A kerion is caused by an allergic reaction to the fungus.

Body ringworm (tinea corporis) may be caused by Trichophyton, Microsporum, or Epidermophyton. The infection generally produces round patches with pink scaly borders and clear areas in the center. Sometimes the rash is itchy. Body ringworm can develop anywhere on the skin and can spread rapidly to other parts of the body or to other people with whom there is close bodily contact.

Beard ringworm (tinea barbae) is rare. Most skin infections in the beard area are caused by bacteria, not fungi.

Treatment

Most ringworm infections, except those of the scalp and nails, are mild. Antifungal creams usually cure them. Many effective antifungal creams can be purchased without a prescription; antifungal powders are generally not as good. The active ingredients in topical antifungal drugs include miconazole, clotrimazole, econazole, oxiconazole, ciclopirox, ketoconazole, terbinafine, and butenafine.

Usually, creams are applied once or twice a day, and treatment should continue for 7 to 10 days after the rash completely disappears. If the cream is discontinued too soon, the infection may not be eradicated, and the rash will return. Ciclopirox in the form of a nail lacquer may be painted on fungal nail infections. This treatment may take up to 1 year, however, and still may not be effective.

Several days may pass before antifungal creams reduce symptoms. Corticosteroid creams are often used to help relieve itching and pain for the first few days. Low-dose hydrocortisone is available over the counter; more potent corticosteroids require a prescription and may be added to the antifungal cream.

For more serious or stubborn skin infections and for scalp and nail infections, a doctor may prescribe an antifungal drug to be taken by mouth. Itraconazole, terbinafine, and griseofulvin are all effective. These drugs are taken daily. Some doctors prescribe fluconazole, which may be given once a week for 3 or 4 weeks for body ringworm. Nail ringworm requires longer treatment with itraconazole or terbinafine: 6 weeks for fingernails and 12 weeks or longer for toenails. Up to 1 year is required for new toenails to grow out. Terbinafine is the most effective drug available for treating nail ringworm. Griseofulvin requires more prolonged treatment. However, nail ringworm does not always respond to drugs taken by mouth and may recur even after apparently successful treatment. Scalp ringworm may need to be treated with drugs taken by mouth for 4 to 6 weeks--or even longer if griseofulvin is used. Some doctors give corticosteroids by mouth to children with a kerion of the scalp.

If the ringworm infection oozes, a bacterial infection also may have developed. Such an infection may require treatment with antibiotics, either applied to the skin or taken by mouth (see Section 18, Chapter 211).

See the sidebar Topical Antifungal Drugs.