Why do we sweat?

Every evening after finishing my yoga session, I leave the yoga studio feeling strong, calm, revitalized, and, above all, incredibly sweaty. The combined effects of a heated yoga studio and physical exertion always seem to challenge my body temperature, resulting in the feeling that every square inch of my skin is oozing with perspiration. My yoga teachers have always told me that sweating is very healthy, and it helps the body get rid of toxins and excess energy. In looking into this question of why we sweat, I will examine the biological basis for sweating, and why it varies from person to person.

Sweating is how the body gets rid of excess body heat, when for example the body is in an environment that is too hot (the heated yoga studio) or is undergoing physical exertion (yoga exercises). People may also sweat when they are sick, experiencing stressful situations, taking drugs, or having hormonal issues, such as an overactive thyroid or menopausal activity. (1) Sweat glands are located in the skin. The glands that produce sweat are inside of the dermis, and a duct runs from the gland to the skin’s surface, where the sweat exits the body through pores. The sweat gland (when stimulated by a rise in temperature, hormone change, physical activity, etc.) produces “sweat,” which is a fluid that mostly consists of water but has a high amount of sodium and chloride and a low amount of potassium. This fluid comes from the spaces in between the cells. After the fluid is secreted, the sweat goes up the duct and out the pore. (2) This process of sweat production varies in intensity throughout the body and according to the conditions under which the glands were stimulated.

There are two types of sweat glands located throughout the body: eccrine glands and apocrine glands. Eccrine glands are located all over your body and open onto the skin’s surface. Aprocrine glands, on the other hand, are found only on parts of the surface where there are hair follicles, such as the underarms, genitals, and scalp. The sweat coming out of each of these glands is different: sweat from the eccrine glands is clear and slightly salty, whereas sweat from the aprocrine glands is thicker and milky, as these glands use fat in part of their secretion process. (3) Given the process by which sweat is produced and the characteristics of such results, we can now ask ourselves why some people sweat more than others.

There are several reasons why the amount of sweat people produce varies among individuals. Genetics are an important factor, as each person is born with a given number of sweat glands (from two to four million). Sex is also a determinant, as “women have more sweat glands than men, but men’s sweat glands are more active, which is why men tend to sweat more than women.” (4) There is another factor, however, which seems to make much more sense to me as to why I sweat so profusely. This fact has to do with the environment to which your body is acclimated. For people whose bodies are not adapted to a hot climate, the maximum amount of sweat that their bodies can produce is around one liter per hour. However, people living in “a hot climate such as the American desert southwest or the tropics” are able to produce about two to three liters of sweat per hour after having been exposed to such a climate for about six weeks. (2)

As someone who definitely sweats above the “normal” rate of one liter per hour, I attribute my ability to produce mass amounts of sweat to having grown up in Arizona most of my life and while in college on the east coast, having spent all of my vacations, summers, and long weekends in the excruciating heat of Phoenix that for four months of the year exceeds 100 degrees and for the rest of the year does not go below 70 degrees on average. Although my genetics and gender probably play a role as well, I find it fascinating that my having grown up in the desert could possibly be big such a big factor in the development of my physical characteristics despite the homogeneity and technology of our modern age. This piece of information has really made me realize to what extent biological creatures (modern-day humans included) respond and adapt so intensely to the environment around them. I never would have expected my excessive sweatiness during yoga sessions to have been even remotely related to my growing up in Arizona.

WWW Sources:

(1) http://www.nlm.nih.gov/medlineplus/ency/article/003218.htm National Institute of Health, definition of sweat.

(2) http://health.howstuffworks.com/sweat.htm “How Sweat Works.”

(3) http://www.cnn.com/HEALTH/library/DS/00305.html “Sweating and Body Odor.”

(4) http://www.aad.org/NR/rdonlyres/66F5C772-07E5-4839-A8D1-868108C58F99/0/DIspring02.pdf#page=12 “Drip or Dry?” Dermatology Insights.