Why do we sweat?

It’s something you probably do every day but don’t give a second thought to: sweat. Whether you’re exercising, making a big presentation at work, or questioning whether or not to call your crush, you’re probably perspiring. So what is sweat, and why is it something we all do?

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Sweat (or perspiration) is a clear liquid (that sometimes contains other substances like fats and proteins) that is produced by glands located in your skin (NIH, n.d.). Sweating is a natural way to regulate your body temperature, and it’s the way your body cools itself down — as sweat evaporates, your body temperature drops. The most common areas where sweat is produced is under the arms, on the feet, on the face, and on the palms of the hands, where many sweat glands are located.

Sweat also serves other functions. The kind of sweat that’s produced by the apocrine glands—more on the different kinds of glands in the next section—is involved in the production of body chemicals called pheromones, which are responsible for body odor, and possibly in social and sexual behavior (Baker, 2019).

Also known as perspiring, sweating is the release of sweat from the glands. It’s a natural bodily process that’s controlled by the autonomic nervous system, the automatic part of your nervous system that controls vital functions like heart rate, blood pressure, and breathing (Low, 2018). Every person is born with anywhere between 2 to 4 million sweat glands, which begin to become fully active during puberty (men’s sweat glands tend to be more active, generally) (NIH, 2019).

There are three types of sweat glands in your body that are responsible for regulating your body temperature: eccrine glands, apocrine glands, and apoeccrine glands (Kobielak, 2015). Eccrine glands are found all over the body and mainly secrete water and electrolytes through the surface of the skin. Apocrine glands are found only in parts of the body that contain hair follicles, like the groin and armpits, and these are the ones responsible for “stress sweat,” which can often smell worse than the watery sweat produced by the eccrine glands. Unlike eccrine glands, apocrine glands produce a thicker, oily sweat that contains proteins, sugars, and ammonia. Apoeccrine glands are basically a mix between the two and do not open into the hair follicle (Sato, 1987). 

There are a lot of reasons your body might perspire. The location of the sweat may depend on what’s causing you to sweat since different sweat glands are located in different parts of the body (eccrine glands are everywhere, concentrated in your palms, soles of your feet, and face, while apocrine glands are mostly in the underarms and genitals; apoeccrine glands are found in the same areas as apocrine sweat glands but produce the kind of watery fluids that eccrine sweat glands do) (Kobielak, 2015). 

Some of the most common reasons people sweat include:

• Increased temperature. Whether the external temperature is up due to hot weather or your internal temperature is up, thanks to heart-pumping exercise, sweat is your body’s natural way of cooling you down. 

• Stress. Stressful situations cause the production of hormones like cortisol and adrenaline, which trigger apocrine glands to release the thick, oily kind of sweat. 

• Certain foods. Spicy foods can obviously raise your body temperature, prompting that need for a cool-down via sweat, but other substances can trigger sweat too. Research has found that caffeine can create an increase in sweating, as can alcohol (Kim, 2011; Yoda, 2005). 

• Certain medications. A variety of prescription and over-the-counter (OTC) drugs can cause sweating as a side effect. Some of these medications include cholinesterase inhibitors, selective serotonin reuptake inhibitors (SSRIs), opioids, and tricyclic antidepressants (Cheshire, 2008). The reasons why certain drugs cause sweating vary—some medications affect the brain, and others affect other parts of the central nervous system that are related to sweating. 

• Hormonal conditions, such as menopause. Changing estrogen levels can influence the production of sweat, so for some women, menopause—a time when estrogen can be all over the place—is unpredictably sweaty. This may be because sex hormones like estrogen and progesterone affect thermoregulation in the brain (Stachenfeld, 2000). Many women experience what are known as “hot flashes,” a sudden feeling of heat and/or flushing in the upper part, or all over the body. These hot flashes can be mild and brief, or strong enough to wake someone up at night (these are called “night sweats”) (NIH, 2017). 

Everyone sweats, but how much is too much? Hyperhidrosis is a medical condition that’s characterized by excessive and unpredictable sweating that may occur even when the temperature is cool, and there’s no physical activity or anything else taking place that might get the heart rate up (NIH, 2019). In some cases, there’s no real explanation for excessive sweating—some people just have overactive sweat glands. Hyperhidrosis does appear to be genetic, though, so if someone in your family has it, you may be more likely to have it too.

There are a lot of medical conditions that can cause hyperhidrosis, like anxiety, hyperthyroidism, cancer, heart disease, stroke, and more. Research indicates that about 4.8% of Americans (approximately 15.3 million people) have hyperhidrosis (Doolittle, 2016). 

To diagnose hyperhidrosis, your healthcare provider may perform tests like a starch-iodine test, which involves putting an iodine solution on a sweaty area and then sprinkling starch on the area after it dries. After it dries, starch is sprinkled on the area, and the iodine-starch combination changes colors from dark blue to black to indicate where there’s excess sweat. Your healthcare practitioner may also want to order other tests like blood tests to help diagnose hyperhidrosis. Based on what you and your provider discuss about your diagnosis, your hyperhidrosis treatment options might include antiperspirants, medications, or even surgery (NIH, 2019).

Hyperhidrosis isn’t the only kind of sweating disorder. Some people don’t sweat enough when there’s an appropriate stimulus like hot weather or exercise—this is called hypohidrosis (or anhidrosis if there’s no sweating at all). Hypohidrosis is rare and can affect the entire body or just part of the body. There are various causes of hypohidrosis, including severe burns, infections, or other skin injuries. Certain medications and health conditions can also cause hypohidrosis (NCI, n.d.). Your healthcare provider will determine whether you have hypohidrosis. Since the condition can lead to overheating, treatment may involve cooling your body with air conditioning or by wearing wet garments on your skin (Merck Manual, 2019).

Whether you have hyperhidrosis or you just want to get a better handle on the amount of perspiration you experience daily, there are plenty of strategies to help manage sweat. 

Bathing regularly is one essential way to wash away bacteria and control body odor. For some people, sweat pads (disposable cotton pads) are helpful to wear under clothes since they absorb perspiration.

Antiperspirant with deodorant is an important tool for many people as well. Antiperspirants work by plugging the sweat ducts. Products that contain 10% to 20% of aluminum chloride hexahydrate are considered the first line of treatment for underarm sweating. There are also prescription-strength antiperspirants available that contain a higher dose of aluminum chloride and are applied every night onto the affected areas. Deodorants by themselves don’t prevent sweating, but they can help reduce body odor. It’s also important to know that antiperspirants do have the potential for side effects like skin irritation, and large doses of aluminum chloride can damage your clothing (NIH, 2019). 

Keeping a food diary may help you identify whether certain foods you’re eating or beverages you’re consuming are causing you to sweat more. Identifying and removing certain foods from your diet (like spicy foods, caffeinated beverages, and alcohol) may help keep perspiration in check. 

Certain medications can sometimes help control excessive sweating. Talk with your healthcare provider about medicines that may help prevent stimulation of the sweat glands in certain areas of the body, like the face. Botulinum toxin (Botox) is sometimes used to treat severe sweating in the underarms, hands, and feet. Botulinum toxin—as well as any other drugs—do carry the risk of side effects, so talk about the pros and cons with your healthcare provider. Sometimes, procedures like iontophoresis, which uses electricity to temporarily turn off the sweat glands in the hands and feet, are appropriate to reduce sweating. In other cases, endoscopic thoracic sympathectomy (ETS), which cuts a nerve, or surgery to remove the sweat glands may be recommended (NIH, 2019). 

To prevent overheating, you may also want to plan your wardrobe to include plenty of layers so you can take off an outer jacket or sweater and keep cool in a lighter shirt or tank top. If you’re sweating a lot throughout the day or during physical activity, you may also want to rehydrate with plenty of water and/or sports drinks that contain electrolytes (NIH, n.d.).

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

February 27, 2020

Written by

Michelle Konstantinovsky

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.