February 10, 2007

Ringworm, Tinea Versicolor


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 Bacterial Skin Infections: Introduction), especially in older people and in people with inadequate blood flow to the feet.

Nail ringworm (tinea unguium, onychomycosis 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 Problems in Infants and Very Young Children: Rashes), 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.


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

Tinea Versicolor

Tinea versicolor (pityriasis versicolor) is a fungal infection of the topmost layer of the skin causing scaly, discolored patches.

The infection, caused by the yeast Malassezia furfur, is quite common, especially in young adults. It rarely causes pain or itching, but it prevents areas of the skin from tanning, producing patches that are lighter in color than surrounding skin. People with naturally dark skin may notice lighter patches; people with naturally fair skin may get dark or lighter patches. The color depends on how the yeast affect the melanocytes, the cells that make the pigment (see Pigment Disorders: Introduction). The patches are often on the chest or back and may scale slightly. Over time, small areas can join to form large patches.

Diagnosis and Treatment

Doctors can diagnose tinea versicolor by its appearance. A doctor may use an ultraviolet light to show the infection more clearly or may examine scrapings from the infected area under a microscope to confirm the diagnosis.

Topical antifungal cream such as ketoconazole may be used, as well as terbinafine
solution spray. Prescription selenium sulfide shampoo is effective if applied full-strength to the affected areas (including the scalp) at bedtime, left on overnight, and washed off in the morning. Treatment is usually continued for 3 or 4 nights. Alternatively, the shampoo can be applied for 10 minutes a day for 10 days. Prescription ketoconazole shampoo is also effective; it is applied and washed off in 5 minutes. It is used as a single application or daily for 3 days.

Antifungal drugs taken by mouth, such as itraconazole, ketoconazole, or fluconazole
, are sometimes used to treat widespread, resistant infection (see Drugs for Serious Fungal Infections). However, because these drugs may cause unwanted side effects, topical drugs are usually preferred.

The skin may not regain its normal pigmentation for many months after the infection is gone. Tinea versicolor commonly comes back after successful treatment because the fungus that causes it normally lives on the skin. Therefore, many doctors recommend use of 2.5% selenium sulfide shampoo or ketoconazole shampoo monthly or every other month to prevent recurrences.

Adapted from: Merck & Co., Inc