The fungi that cause athlete's foot thrive in warm, moist areas. Susceptibility to this infection is increased by poor hygiene, occlusive footwear (closed-up shoes, such as tennis shoes), prolonged moist skin and minor skin or nail injuries. Fungi reproduce by creating spores (seeds, for want of a better description), and these spores can stay dormant in shoes, socks, bath mats and floors and, even if the surface is cleaned, they can remain viable and infect people at a later stage.
Tinea infections are contagious and can be passed through direct contact, or contact with items such as shoes, stockings, and shower or pool surfaces (because of the spores). They also can be transmitted from contact with pets that carry the fungus. Athlete's foot may be brief or long-term and may recur even after treatment.