Athlete's foot is a very common skin infection of the foot caused by fungus. The fungus that commonly causes athlete's foot is called Trichophyton. When the feet or other areas of the body stay moist, warm, and irritated, this fungus can thrive and infect the upper layer of the skin. Fungal infections can occur anywhere on the body, including the scalp, trunk, extremities (arms and legs), hands, feet, nails, groin, and other areas.
Athlete's foot is caused by the ringworm fungus ("tinea" in medical jargon). Athlete's foot is also called tinea pedis. The fungus that causes athlete's foot can be found on many locations, including floors in gyms, locker rooms, swimming pools, nail salons, and in socks and clothing. The fungus can also be spread directly from person to person or by contact with these objects.
However, without proper growing conditions (a warm, moist environment), the fungus may not easily infect the skin. Up to 70% of the population may have athlete's foot at some time during their lives.