Sweat, or more formally perspiration, is a saline liquid excreted by the sweat glands through the pores of the skin of humans in order to regulate body temperature. All mammals produce sweat, but humans are one of the few mammals that produce sweat all over their bodies. However, sweat is produced more readily under the arms, on the palms of the hands, on the soles of the feet, and on the forehead.
Sweat cools the body through evaporation. When the water in sweat turns from liquid to vapour, it absorbs heat in order to turn into a gaseous state. This process is inhibited by high levels of humidity in the air, which slow the evaporation rate. It is also interrupted by clothing that does not readily absorb water. However, a body will sweat in response to a number of factors in addition to overheating, such as emotional discomfort. Fever is almost always accompanied by sweating and a sweating patient in an otherwise temperate environment should be checked for fever.
Human beings have a wide variety of sweat response, which is completely autonomic and is controlled by the hypothalamus. However, on average, men tend to start to sweat sooner than women. People who have recently spent a long time in a hot climate will also sweat more readily than those who have recently spent a long period of time in a cool climate.
Excessive sweating will lead to dehydration if an individual does not replace the water.
Some medical conditions, such as CIPA, leave an individual unable to sweat.