Tinea cruris, commonly referred to as jock itch, is a fungal infection in the groin area, affecting mostly adult men. It's caused by a type of fungus called dermatophytes. It grows in a circle on your skin and often looks like a ring. Because of inflammation, the skin becomes red.
Some people think the infection looks like there is a worm under the skin. Because of this, this infection is often referred to as "ringworm," although no worm is actually involved. The fungi are commonly found on the skin surface and nails and are usually quite harmless. Under certain conditions, however, they can multiply, causing inflammation and surface tissue damage.
You don't have to be athletic to get jock itch. Infections caused by dermatophytes go by the medical name tinea. Tinea pedis is athlete's foot; tinea capitis is ringworm of the scalp. Jock itch is tinea cruris, from the Latin word for leg. They are all caused by the same organisms – only the infected area differs.
Classic jock itch affects the inner thighs, groin, and lower buttocks, not the genitalia themselves. If the scrotum is inflamed, it's probably due to a different yeast condition called candidiasis, and a physician should be consulted.
Dermatophytes like to grow on skin that's moist and warm and thrive in areas where skin comes into contact with other skin, such as the groin or between the toes. Overweight men are more likely to develop jock itch if they sweat a lot or have folds of touching skin. Tight clothing and hot, humid weather are other risk factors.
Men who play sports and use a male athletic guard are particularly prone to tinea infections. Sweaty equipment left in a locker makes an ideal environment for tinea to grow. The fungi can live on towels, floors, carpets, and toilet seats. Sharing towels, combs, and shoes can easily transmit fungal infections.
Since the same organisms can cause tinea in different locations, it is not uncommon for someone with athlete's foot to get jock itch by toweling his feet before his groin.