Athlete's foot and fungal nails are the most common fungal problems with feet. A fungus is a common mold that thrives in dark, warm moist areas. On the feet, it can grow on and between toes, as well as on soles and toenails. Fungal problems can be a result of the environment (socks, shoes, heat and humidity) or weakened immunity from such disorders as diabetes.

Chronic fungal infections are most common in adults, while acute fungal infections are seen more often in children.