(See also Overview of Fungal Skin Infections.)
Dermatophyte infections are sometimes called ringworm or tinea. Despite the name, a ringworm infection does not involve worms. The name arose because of the ring-shaped skin patches created by the infection.
Dermatophytes are molds (a type of fungi) that need the protein keratin for nutrition. Keratin is the structural material that makes up the outer layer of human skin. It is also the main structural material of hair and nails. To survive, dermatophytes must live on skin, hair, or nails (a nail infection is called tinea unguium or onychomycosis).
Infection may occur almost anywhere on the skin, including the
A dermatophyte infection on one area of the body can cause a skin eruption to appear on another area of the body that is not infected (see Dermatophytid Reaction).
Dermatophyte infections in humans are caused by Epidermophyton, Microsporum, and Trichophyton. These organisms may inhabit a person permanently and never cause an infection. When they do cause an infection (resulting in ringworm or tinea), it is often because the affected area's blood supply is poor or because the person's immune system is suppressed (for example, by diabetes, cancer, or HIV infection). Unlike candidiasis, these fungal infections cannot infect internal organs or blood.
Symptoms of a dermatophyte infection vary depending on the location of the infection. Most often, there is little or no inflammation and the infected areas are mildly itchy with a scaling, slightly raised border. These patches can come and go intermittently. Occasionally, inflammation is more severe and suddenly causes large and small fluid-filled spots to appear (usually on the foot) or an inflamed, swollen patch on the scalp that sometimes oozes pus (kerion).
Doctors can frequently identify a tinea infection by its appearance.
To confirm the diagnosis of tinea, doctors take skin scrapings and view them under a microscope. Doctors do a culture of the scrapings (the process of growing an organism in a laboratory for identification) only if the person has a scalp or nail infection. Identifying the type of fungus helps doctors choose the best treatment.
Treatment of tinea varies by site but always involves antifungal drugs that are applied to the affected area (topical) or are taken by mouth. (See also table Some Antifungal Drugs Applied to the Skin (Topical Drugs).)
Corticosteroids may be given to relieve itching and inflammation.