Sweat, also called perspiration, is a fluid produced by the sweat glands made up of water, minerals, lactate and urea. The minerals that make up sweat can vary from person to person depending on a number of factors. This fluid is used by the body to help cool it when heat builds up inside.
A number of factors influence the types of minerals that are produced in sweat such as a person's acclimation to heat. The more a person is exposed to heat, the more their body adjusts to keep the minerals it needs and remove what it does not. Similarly, the amount of time needed to cool a person's body off can also affect what minerals are released. Minerals found in sweat include sodium, potassium, calcium and magnesium as well as a number of other trace elements such as zinc, copper and chromium.
In addition to humans, all other mammals sweat. However, unlike some species, human sweat is hypoosmatic, meaning it is less salty than plasma. Like horses, humans also produce more sweat than most species of mammals to regulate body temperature. Other species, such as dogs, reduce their body heat by panting and other means.