Feeling soggy may not seem like a superpower, but the human ability to perspire is regarded as an evolutionary marvel and one of our most distinctive traits. Sweat serves as a highly efficient internal air conditioner, vital to regulating core temperature. Though we experience this natural phenomenon every day, the mechanism remains widely misunderstood. Here, we pore over the science behind the body’s incredible cooling system.
WRITTEN BY Stratton Lawrence
PHOTOGRAPHS BY Scott Henderson
Life in Charleston is inherently sweaty—springtime highs can reach the mid-80s and 90-degree days are the summertime norm. Fortunately, people have a natural advantage over the animals with which we share the humid Lowcountry. On a steamy day, dogs must pant to expel hot air. Pelicans have to flutter their throat pouches. Alligators chill with a swim. Humans, on the other hand, sweat.
We’re joined by only a few members of the animal kingdom—including monkeys, apes, hippopotamuses and horses—that possess this superpower. And though we may not win the 100-yard dash against a cheetah, we could prevail in a marathon. That’s because humans’ ability to stay cool gives us the endurance to cover long distances without overheating.
While most of us aren’t running marathons every day, sweat sessions are hopefully a regular part of your fitness routine. To better understand the purpose behind perspiration, as well as other benefits it may present, we asked Roper St. Francis Healthcare affiliated primary care physician Dr. Valerie Scott and dermatologist Dr. Todd Schlesinger to turn up the heat on this critically important function. In the following pages, these experts explain why sweat stinks (spoiler: it doesn’t), offer advice on how to put armpit sweat in check and give tips for staying cool and safe all season long.
The Perspiration Situation
Sweating is an evaporative cooling process that works much like our refrigerators and air conditioners—when moisture rises to the surface and comes into contact with the air, we experience immediate relief (even if it doesn’t feel that way mid-workout). To understand how evaporative cooling works, stand in front of a fan. Then go for a run and come back. The air from the fan will feel even cooler as it whisks the moisture away from your skin. Without this mechanism, we couldn’t do outdoor chores or go for a walk when it’s hot outside.
There’s not much to sweat—it’s simply water from our bloodstream that’s released through the pores in our skin. Sweat also contains salt and sugar (the amounts vary between individuals), along with traces of ammonia and urea generated when our cells break down proteins.
Several million sweat glands under our skin’s surface help to draw water out of our bodies. The majority of these are eccrine sweat glands, which release sweat directly to the surface of the skin. Found all over the body, from your feet to your face, they’re the main sweat glands responsible for regulating body temperature. Sweat from eccrine glands is primarily water and doesn’t have a smell.
The rest are apocrine glands, which release sweat into hair follicles and are found in the armpits, around the groin and on the scalp. Sweat from apocrine glands contains proteins and lipids, which make it oily and help keep our hair smooth and glistening. These glands kick on when we hit puberty—about the time we start to generate funky smells. But it’s not the sweat that actually stinks—body odor comes from bacteria that live on our skin and feed on sweat.
Although most people find these smells unpleasant, they likely play a biological role. “Sweat is one of those evolutionary marvels that helps us live longer,” Dr. Schlesinger explains. “The odor particles and proteins in our sweat evolved to help us attract mates.” Of course, any role bacterial odors once played in sexual attraction has been suppressed in our showered, freshly scented society.
Breaking a Sweat
While sweat is critical to keeping us cool, its benefits beyond temperature regulation, such as losing weight or shedding toxins, are marginal and less understood. “Sweat is one way to metabolize toxins in our bodies, but it’s far from the most efficient,” explains Dr. Scott, who also acts as the Burke High School football team doctor. The liver and kidneys are the body’s first line of defense for shedding chemicals and metals, with sweat kicking in as a last resort.
If you’ve ever consumed too much alcohol and felt like you were sweating it out the next day—or worse, someone smelled it on you—then you know the role that sweat can play when your other organs become overwhelmed. (Exacerbating the effect, alcohol dilates blood vessels and increases heart rate, fooling your body into thinking you’re exercising and inducing a cooling sweat.)
In healthy people who don’t overdrink or have kidney issues, sweat isn’t a primary means of toxin expulsion. “We have backups for our backups,” Dr. Scott explains, emphasizing how low sweat falls in the order of detoxification. That doesn’t mean diet won’t change our sweat. Eat a plate of fiery Szechuan noodles, and your eccrine glands will kick into overdrive trying to cool your body down. Or go heavy on garlic, onions, cabbage or Brussels sprouts, and the sulfur in these veggies may surface in your body odor. From a health standpoint, that’s neither good nor bad, just an interesting phenomenon.
More sweat also doesn’t automatically mean better health. “Being soaked after a workout may prove you’ve worked hard, but sweat quantity doesn’t correlate to weight loss or a cardiovascular boost,” says Dr. Scott. There’s no reason to try to sweat more when you work out, because you’re just shedding water. An extra jacket on a run (or athletes hustling through sprints in plastic trash bags) doesn’t drop extra pounds—you’ll simply lose more water and potentially risk dehydration. “The benefit is in the exercise, not in the sweating.”
The same is true of saunas. While sitting in a hot room feels good, opens up your pores and can help you relax, the practice won’t help you shed weight or significant toxins. Dr. Schlesinger also cautions against taking steps to increase sweat during a workout, especially for people on medications that reduce sweating. “Body temperature rising over 103 degrees can cause heatstroke and loss of consciousness,” he explains. “It’s best not to mess with the body’s natural mechanics.”
Our “normal” amount of sweat is determined by body mass. Men typically sweat more than women, because they tend to have more muscle and greater body mass, leading to a higher internal temperature. But all bodies are built differently, and that includes cooling systems.
Some people begin to sweat so much during puberty that it impairs social development. For others, this over-sweating condition, known as hyperhidrosis, may begin later in life. Excess sweat is also often seen in menopausal women and people who are overweight. “The biggest concern with hyperhidrosis is the social aspect,” says Dr. Scott. Although sweat can be collected and weighed for a formal diagnosis of hyperhidrosis, “too much” sweat is typically subjective—if perspiration is hindering your life, talk to your doctor.
The most common sweat-related disorder is primary focal hyperhidrosis in the armpits, due to an abnormality in the autonomic nervous system (that part of the nervous system that controls digestion, blood pressure and other organ functions). This problem can be due to genetics, as some families sweat more than others, or the environment. Charleston transplants may only notice an issue after relocating here from a colder climate. “If you grew up in Minnesota then moved down here, you probably sweat a lot more now than you’re used to,” says Dr. Scott.
Medications can also lead to hyperhidrosis. Selective serotonin reuptake inhibitors (SSRIs) like Prozac, Paxil and Zoloft may have the side effect of increased sweating. Hormones to stimulate underactive thyroids are another common cause, and excessive perspiration may indicate too high a dose.
Sweating the Details
“Sweat is the body’s temperature regulatory mechanism,” explains Dr. Schlesinger. Because of that, medical measures to control sweat are approached with care. The two most common direct treatments are Drysol, a prescription aluminum chloride deodorant, and Qbrexza, an anticholinergic underarm wipe that blocks the signals triggering sweat. Some patients require an oral medication like Robinul, a peptic ulcer treatment that reduces sweat and saliva levels. These patients have to be diligent to avoid heatstroke, since they lose some ability to self-regulate temperature.
In severe cases, including overly sweaty hands, Botox injections work to block the nerve signals causing sweat. Newer treatments such as microwave rays and tiny clips on nerves are also being used. As a last resort, doctors may surgically remove apocrine sweat glands, especially in cases where inflammatory disease, nodules or cysts accompany the hyperhidrosis.
Although far less common, some people have the opposite problem: anhidrosis. Conditions like Sjogren’s and Guillain-Barré syndromes can damage sweat glands, as can burns and extreme dehydration. Alcoholism and opioid abuse can also lead to a diminished ability to sweat. Without the ability to regulate internal temperature, people with anhidrosis are more likely to suffer heatstroke and must be vigilant about staying cool when it’s hot outside.
“When you live in South Carolina, perspiration is just a part of life,” says Dr. Scott. “Sweat is normal, and it’s a good thing.” So unless your body isn’t cooling as it should or excessive perspiration is hindering your social or work life, don’t sweat it.
57, James Island
PROBLEM: As a professor who regularly stands in front of large groups, Lisa Deaton felt insecure about her excessive sweating. “The wetness under my arms really limited my attire and made me uncomfortable,” she says.
TREATMENT: After raising the issue with her primary care doctor, Lisa learned she had a common condition known as hyperhidrosis. For about a month, she used Drysol, a prescription antiperspirant, to treat the problem. The ambitious runner now relies on exercise and plenty of hydration to relieve stress and regulate her sweating.
67, North Charleston
PROBLEM: Around age 50, Dennis Connolly noticed that he was sweating more than usual. “Mostly under my arms, but also down my lower back. I would sweat so much that it would ruin my shirt,” he recalls. As the owner of a landscaping company, he regularly worked outside in the heat, which exacerbated the issue.
TREATMENT: Dennis talked to his primary care doctor, who prescribed glycopyrrolate to treat the hyperhidrosis. While the pills helped, Dennis still had excessive perspiration under his arms, so he began getting Botox injections to stop his armpits from sweating. “Now, the only time I have extra sweating is if I’m stressed,” says the retired landscaper, who still spends most of his time outside, fixing up his two-acre property along the Ashley River.
For Sweat’s Sake
Sweating can certainly make us feel healthy. A sauna session often relaxes muscles, eases the mind and reduces stress. It may also increase heart rate, which is good for short periods. The same can be true of exercise done in a hot environment, such as Bikram yoga.
What extra sweat doesn’t do is cause weight loss (other than temporary water weight) or lead to a significant amount of detoxification. “Exercise-induced sweat tells you that you’re performing at a higher level, but the extra sweat doesn’t actually do anything beyond keep you cool,” says Dr. Valerie Scott.
While working out in the heat and humidity can certainly leave us dripping with good feelings, exercising when the thermometer’s high carries increased risks of dehydration and heatstroke. Be sure to drink extra water, and listen to your body if you feel faint or overly exhausted.
Grossly Fascinating Facts
The human foot is home to 125,000 sweat glands—the most inch for inch in the human body—and can produce half a pint of sweat each day. No wonder our shoes stink!
Sweat isn’t always clear. Certain antibiotics can cause red sweat, and a condition called chromhidrosis produces sweat ranging from green to black. Copper miners’ sweat may also appear blue when the mineral interacts with moisture.
In a high-sweat environment, fluids swallowed through the mouth can emerge through the skin as sweat in as little as 15 minutes.
A blind study in the journal Chemical Senses found that women prefer the body odor of vegetarian men over that of carnivores.
Stress sweat differs from regular sweat. Regular sweat cools with a quick-drying combo of water, salt and potassium. The fatty acids and proteins in stress sweat evaporate more slowly, feeding odor-causing bacteria.
Which is right for you?
Although the two are often sold as all-in-one products, deodorants and antiperspirants actually differ:
Deodorants make your skin acidic and, thus, less attractive to the bacteria that cause body odor. You’ll still sweat, but you’re less likely to smell bad.
Antiperspirants use aluminum-based compounds that plug pores and stop the flow of sweat for a day or more. Since most sweat occurs through eccrine glands rather than the apocrine glands in our underarms, blocking sweat in this localized area isn’t detrimental to overall temperature regulation.