Jock itch, also called tinea cruris or ringworm of the groin, is an infection of the groin area caused by fungus.

The body normally hosts a variety of bacteria and fungi. Some of these are useful to the body. Others can multiply rapidly and form infections. Jock itch occurs when a particular type of fungus grows and multiplies in the groin area.

Jock itch occurs almost exclusively in adult men. It can sometimes accompany athlete's foot and ringworm. The fungus that causes jock itch thrives in warm, moist areas. Jock itch can be triggered by friction from clothes and prolonged wetness in the groin area (such as from sweating).

Jock itch may be contagious. It can be passed from one person to the next by direct skin-to-skin contact or contact with unwashed clothing. Jock itch usually stays around the creases in the upper thigh and does not involve the scrotum or penis. It is often less severe than other tinea infections, but may last a long time. Jock itch may spread to the anus, causing anal itching and discomfort.

Other causes of itching in the groin include:

• Lichen simplex chronicus
• Eczema
• Pubic lice
• Chemical irritation

See also: Vaginal itching

• Itching in groin, thigh skin folds, or anus
• Red, raised, scaly patches that may blister and ooze -- The patches often have sharply-defined edges and are often redder around the outside with normal skin tone in the center
• Abnormally dark or light skin

Your doctor will usually diagnose jock itch based on the appearance of the skin. Tests are usually not necessary. If tests are needed to confirm the diagnosis, either a culture or a skin lesion biopsy (for example, a scraping of the skin) may show the fungus that causes jock itch.