Jock itch (tinea cruris) is a pretty common fungal infection of the groin and upper thighs. Jock itch is also sometimes called crack fungus, crotch itch, bag rot or crotch rot, dhobi itch (after Indian washermen). It is a common fungal infection that affects the skin of your inner thighs, buttocks and genitals. Men and women encounter the disease worldwide, although it is seen more often in the humid tropics.