There is a good reason why humans sweat more in the summer: heat. The summer brings hot weather, and depending on where someone lives, the heat they are exposed to can be significant. But why does heat make people sweat?

Humans are designed to maintain an internal body temperature within a narrow range of temperatures between 91.76 and 100.76 degrees fahrenheit. When humans are exposed to high external temperatures their body has to work in order to cool itself down and keep its internal temperature within a safe range. The main way the body does this is by sweating. Sweat works with body temperature in a way that it allows the body to cool itself down. The body’s ability to regulate its internal core temperature is called thermoregulation and that process is what initiates sweating.[1]

Sweating is the only automatic process the body has to cool itself down which makes it critical for survival. When a person is exposed to high temperatures the body initiates sweating. The brain senses that a person’s internal temperature is beginning to rise in response to their environment and it activates the sympathetic nervous system. This is a branch of the nervous system that is responsible for activating automatic bodily functions, including the “fight or flight” response. The sympathetic nervous system is attached to eccrine sweat glands via sympathetic cholinergic fibers which activate the sweat glands. Eccrine sweat glands are located all over the body and they are where sweat is produced and pumped onto the surface of the skin. There is another type of sweat gland, called apocrine sweat glands, but they are not thought to be used in thermoregulatory processes. When sweat glands are activated, vasodilation (expanding of the blood vessels) begins and sweat glands begin taking liquid from blood vessels and secreting it onto the surface of the skin. Sweat is made of water, for the most part, and once sweat is on the skin it is rapidly evaporated off into the surrounding environment as water vapor. When sweat leaves the skin it carries heat energy with it that was previously inside the body, thus cooling the body down. When the body has cooled itself enough the brain sends signals to the sweat glands to stop producing sweat and the process is halted.[1]

This is all a normal part of why humans sweat, and it is part of what allows to exist in so many varied environments on the planet. Without the ability to sweat, summer would be a lot more deadly.

Sources
  1. Tansey, E. A., & Johnson, C. D. (2015). Recent advances in thermoregulation. American Physiological Society. Retrieved April 18, 2019, from https://www.physiology.org/doi/full/10.1152/advan.00126.2014.