Possible causes of toe fungus include wearing damp shoes or socks and exposure to humid, warm conditions, according to Mayo Clinic. Fungi can live in moist household environments, such as swimming pools or showers.
Athlete's foot is a common type of toe fungus that a person can contract by interacting with someone who has it, as athlete's foot is contagious, states Mayo Clinic. A person can also become infected with athlete's foot fungus by bumping into or walking on a surface supporting the fungus, such as a floor or a towel. The same type of fungus also causes ringworm and jock itch, so it is important to avoid people infected by either condition.
A dermatophyte fungus is often the cause of a fungal infection in the toenail, notes Mayo Clinic. Fungi do not need sunlight to survive, making shoes or socks a common breeding ground. Fungi can enter the skin through microscopic cuts or through the tiny separation between the nail bed and the toenail.
Because toes do not receive as much blood flow as other body parts, such as the fingers, the body's immune system may have a difficult time fending off a fungal infection in the toes, according to Mayo Clinic. Certain types of molds or yeasts can cause nail fungal infections.