Foot fungus is a skin infection caused by mold-like germs that live in dead cells on your skin, hair, and nails. There are more than 80 types of fungi on your feet. That's more than on other parts of the body, even the palms of your hands. But while some of these fungi may get a bad rap, most aren’t harmful. Athlete’s foot is the most common type of foot fungus. Up to 25% of people will get this itchy, even painful infection at some point. It usually grows between the toes but can spread to the soles and toenails. If you scratch your foot and then touch other parts of your body, like your armpits or groin, it can spread there, too.