Tinea refers to infection of the outside surface of the skin by fungus, specifically a type of fungus known as a dermatophyte. These fungi can live only on the outer surface of the skin, and cannot invade the body. However, they can live and grow on the skin surface, literally consuming the proteins of the outer skin surface for nutrition. Heat and moisture, such as found on a sweaty foot, are perfect conditions for the fungus to grow.
Depending on where the fungus infection lies, the patterns are different. On the feet, tinea results in typical athlete’s foot. If the infection is on the body or extremities, it will form a round, gradually expanding scaly patch, leading to the common name ringworm (though it is not, of course, caused by a worm). On the scalp, it produces scaling and crusting, and eventually hair loss.
Treatment for mild cases can be done with topical antifungal creams. More severe cases, particularly those infections in hair-bearing areas like the scalp, can be more difficult to treat and often require longer courses of oral antifungal medications.