Then there are the apocrine glands, which are triggered by emotional stimuli, not heat. Sweat that is the result of heat is colorless and odorless - or so the scientists say. The body's effort to cool itself begins when you walk outside on a hot day. Capillaries in the skin dilate, filling with blood and expanding their surface area to dissipate heat. The sweat glands draw off water from the blood to bathe the skin, keeping the body temperature within normal limits.
Humans are the only animals whose skin is laced with such an extensive network of capillaries.
Rabbits have them but only in their ears. Dogs have them but mostly in their tongues and paws. The capillaries in their skin can't dilate or constrict enough to control the flow of water to the surface. Men sweat more than women, Kenney says, because women are better able to regulate the amount of water they're losing. This is particularly important on humid days when sweat doesn't evaporate as readily or cool the body as efficiently.