There are more than two and a half million eccrine sweat glands all over the body. They lie deep in the skin and are connected to the surface by coiled tubes called ducts. Sweat (perspiration) is a liquid mixture made up of 99% water and 1% salt and fat. Up to a quart of liquid a day can evaporate through the sweat glands.

As the body becomes overheated, a person sweats, which evaporates and cools the body. When a person becomes frightened or nervous, like being pinned under heavy weights, the body begins to sweat on the palms and forehead, as well as the soles of the feet and in the armpits. These are the sites where sweat glands are most abundant.