Excessive sweating of the feet is called hyperhidrosis. It's more common in men than in women, and more common in young adults than older adults. Excessive sweating of the feet seems to be an inherited problem. No one knows exactly why it occurs, but people who sweat excessively seem to have a different “set point” than other people. Most people sweat when it's hot out, or when they become warm. People with hyperhidrosis sweat excessively almost all the time.