Sweat is produced by dedicated sweat glands, and is a mechanism used primarily by the body to reduce its internal temperature. There are two types of sweat gland in the human body, the eccrine gland and the apocrine gland. The former regulates body temperature, and is the primary source of excreted sweat, with the latter only secreting under emotional stresses, rather than those involved with body dehydration.
Eccrine sweat glands are controlled by the sympathetic nervous system and, when the internal temperature of the body rises, secrete a salty, water-based substance to the skin’s surface. This liquid then cools the skin and the body through evaporation, storing and then transferring excess heat into the atmosphere.
Both the eccrine and apocrine sweat glands only appear in mammals and, if active over the majority of the animal’s body, act as the primary thermoregulatory device. Certain mammals only have eccrine glands in specific areas – such as paws and lips – warranting the need to pant to control their temperature.