Sweat cools people off by taking advantage of the fact that water absorbs heat when it evaporates, according to Georgia State University. Per the university, water has a very high heat of vaporization, meaning that water requires a relatively large amount of heat to change into its gaseous state. This imparts a cooling effect on the person who is sweating.
According to New Mexico University, sweat contains electrolytes dissolved into water. Demonstrating the body’s reliance on sweat to cool it, the University of New Mexico states that the average human has about 2.6 million individual sweat glands. During periods of intense exercise, the average human can lose up to two litters of water per hour. However, according to Medline Plus, some people have a condition called hyperhidrosis, which is characterized by excessive and unpredictable sweating. Fortunately, the condition is only estimated to afflict less than 3 percent of the population.
Because sweat must evaporate in order to cool a person, sweating is not as beneficial a mechanism when the relative humidity is high. However, under normal circumstances, the Georgia State University states that sweating and the evaporative cooling that it produces, represents a very important mechanism for cooling the human body.