in: Health, Health & Fitness, Podcast

• Last updated: March 14, 2022

Podcast #724: The Strange Science of Sweat

Start jogging around the block, or simply sitting outside on a hot summer day, and you begin to feel moisture develop all over your body. Maybe a drop of sweat will roll down your face. Your clothes get sticky. You start feeling in greater intensity a process that’s actually going on all the time: sweating.

You may never have thought too much about your sweat, or perhaps been a little embarrassed by it when your sweat became noticeable in a socially delicate situation. But my guest today says that human sweat is in fact incredibly fascinating, and something you should embrace with real appreciation and enthusiasm. Her name is Sarah Everts and she’s a science journalist and the author of The Joy of Sweat: The Strange Science of Perspiration. Sarah and I begin our conversation with what sweat is, the two kinds your body produces, and how human sweating is unique and what Sarah calls our species’ superpower. We then get into the surprising quickness with which the things we drink start coming out of our pores, why we sweat when we’re anxious or nervous, whether how much you personally sweat comes down to genetics or environment, and why the fitter you are, the more you sweat. Sarah unpacks whether there are differences between how men and women sweat and smell, whether our dislike for body odor is innate or culturally conditioned, why some people are smellier than others, and the role that smell and pheromones play in attraction. Sarah also explains whether antiperspirants are bad for you and if you should switch to natural deodorant. We end our conversation with why it feels so good to make ourselves intentionally sweat through things like sauna-ing, and whether hitting the sauna can detox your body.

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Brett McKay: Start jogging around the block or simply sit outside on a hot summer day and you begin to feel moisture develop all over your body, maybe a drop of sweat will roll down your face, clothes start to get sticky, you start feeling in greater intensity a process that’s actually going on all the time, sweating. You may have never thought too much about your sweat or perhaps been a little embarrassed by it when your sweat becomes noticeable in a socially delicate situation. But my guest today says that human sweat is in fact incredibly fascinating, it’s something you should embrace with real appreciation and enthusiasm. Her name is Sarah Everts, and she’s a science journalist and the author of The Joy of Sweat: The Strange Science of Perspiration.

Sarah and I begin our conversation with what sweat is, the two kinds your body produces and how human sweating is unique, and what Sarah calls our species’ superpower. We then get into the surprising quickness with which the things we drink start coming out of our pores, why we sweat when we’re anxious or nervous, whether how much you personally sweat comes down to genetics or environment and why the fitter you are, the more you sweat. Sarah unpacks whether there are differences between how men and women sweat and smell, whether our dislike for body odor is innate or culturally conditioned, why some people are smellier than others, and the role that smell and pheromones play in attraction. Sarah also explains whether antiperspirants are bad for you and if you should switch to a natural deodorant. And we end our conversation with why it feels so good to make ourselves intentionally sweaty, through things like a sauna, and whether hitting the sauna can detox your body. After the show’s over, check out our show notes at


Brett McKay: Alright, Sarah Everts, welcome to the show.

Sarah Everts: It’s great to be here.

Brett McKay: So you’ve got a book called, The Joy of Sweat: The Strange Science of Perspiration, and this book had you traveling around the world, talking to scientists about sweat. So how did that happen? How did you end up traveling the world? And you went to Germany, I think. You went to different countries, I think Russia at one point, to research about sweat. How’d that happen? 

Sarah Everts: Well, I’m a science journalist, and a long time ago I was a chemist, but I’m also a person who is always slightly afraid that I might sweat a little bit too much, and at some point I decided, “You know, let’s just dig into the research on sweat instead of being anxious about it.” And so, yeah, I tracked down people who are doing scientific analysis of sweat, and then also people who are playing around with cultural taboos, and yeah, for example, that’s how I ended up in Moscow at a sweat dating event.

Brett McKay: And so, something you highlight in the book is that sweat is something we all do, but sweat has pretty much gotten the short shrift in scientific research. What’s going on there? Why is that? 

Sarah Everts: Yeah, it’s really interesting because if you just look at the scientific literature, you see that compared to, say pee, sweat has an order of magnitude, less articles about it, and you wonder if scientists just wondered if it was just salt and water. And actually, sweat is so much more interesting than that, because it’s sourced from the watery parts of blood, pretty much anything that’s circulating around in your blood system emerges out in sweat because your sweat glands, once the big things in blood, like red blood cells, platelets, immune cells are filtered out, all that liquidy stuff gets dispatched to your skin when you’re too hot.

Brett McKay: Alright, okay, so that’s interesting. We’ll talk more and then what makes up sweat, but that was something I learned. What is sweat? Well, it’s salt and water ’cause we’ve all tasted our sweat probably, but I didn’t know it came from your blood, it was just basically your blood.

Sarah Everts: Yeah, it’s the liquidy parts, so effectively you have, that’s called blood plasma. And when you cut open a body, I don’t mean that in a horrific way. Our bodies are wet inside, there’s moist liquid around all of our organs, that’s called interstitial fluid, and so interstitial fluid comes from blood plasma, that liquidy parts of blood, and then when we overheat and our sweat glands get the big directive to open the flood gates, well, what do they do? They go to that interstitial fluid and they dispatch it to the surface because when you evaporate water, this consumes heat, and so the sweat evaporation effectively whisks heat away from your hot body and out into the atmosphere.

Brett McKay: You also mentioned in the book, okay, sweat is primarily salt and water, but there are two types of perspiration, you have two types of sweat pores, what are those two types of sweat pores and what’s the difference between the sweat that comes out of each one? 

Sarah Everts: Out of our sweat pores that cover our body, we have about 2 to 5 million. I have three million sweat pores. That is called eccrine sweat, and that’s that liquidy part of the blood that’s responsible for helping us cool off. But there is another kind of sweat gland and that’s the one that appears in armpits at puberty, it’s called the apocrine gland, and its sweat is actually not watery or salty at all, it’s very waxy, it’s actually pretty similar to earwax, and when that sweat starts coming out anywhere where hair grows at puberty, bacteria living in your armpits eat it, and it’s their metabolites, effectively bacteria poop, that is that stinky smell that starts wafting out of armpits from the teenage years onward.

Brett McKay: We’ll talk a little more about BO here in a bit, but do we know why we have that special armpit gland? Why do we sweat that? What’s the purpose of it? 

Sarah Everts: Right, that’s stymied scientists for a long time but many think that it does have to do with what’s called chemical communication, or odorous communication; that this is a way that we share information about ourselves to other humans, and it probably had more of a role earlier in our evolutionary history, but it’s like vestigial, it’s still there around. And then, of course, some people speculate that it’s involved in sexual maturation, that it is somehow involved in love, or at least romance, because it appears at puberty when everything else gets cracking for procreation.

Brett McKay: Alright, and that connects to the subject of pheromones, and we’re gonna talk about that here in a little bit. But let’s talk about the idea of sweating in the animal kingdom in general, so all animals have to keep themselves cool somehow because just living creates heat through metabolism, and if you don’t cool yourself off, you’re gonna die. But the way humans cool off with sweat is different from other animals. How so? 

Sarah Everts: Right, so sweating as much as it’s kind of gross to a lot of people is actually our superpower in the animal kingdom, it’s one of the things that makes us unique along with nakedness. And the reason it’s such a superpower is that it allows us to cool down while we’re on the move, so if you can imagine in our history, many of the prey that we needed to hunt, sprints faster than us, but because we have this huge surface area for evaporating off water, getting rid of our body heat, we can cool down while on the run. And so our prey sprints away super fast, but then they have to stop and cool down because death by heatstroke, a terrible way to die. And eventually we can catch up forcing them to sprint away, and sprint away, and sprint away until they’re so weakened by heatstroke that they’re easy to kill or to hunt. And what’s so amazing about humans is our naked skin surface. So if you think about a dog panting, we all know that’s how dogs cool down, it is evaporating away water because that’s the best way to cool your body down, but it’s doing it off the only naked surface that it has, it’s tongue. And instead, humans have our whole bodies to do that on, and even chimpanzees our closest evolutionary neighbor or relative, although they have sweat glands over their whole bodies, many, many primates do, not all, but some, they are cooling down by panting because our naked bodies have that surface area.

Sarah Everts: And the modern incarnation of this is we can run marathons, we’re really good at not dying of heatstroke while we’re exercising heavily.

Brett McKay: Yeah, we had Daniel Lieberman on the podcast, and I think you talked to him.

Sarah Everts: Oh, he’s great. Yeah.

Brett McKay: Yeah, and he talked about… He’s done a race with horses, so it’s like a long distance race where he raced a horse. And in the beginning the horse was beating him, but eventually the humans all beat the horses because the humans can keep going ’cause the horse had to stop, ’cause they overheat and they have to cool down.

Sarah Everts: Exactly, and what’s kind of also amazing is that because this evaporation of water is so important for staying cool, animals dispatch other bodily fluids, what do they have available to the surface of their bodies to get rid of heat. And dogs use saliva, but seals rely on urine, honeybees vomit on themselves all to get their bodies wet so that it can away heat. And the thing about humans is, A, we’ve got specialized glands just to do this, number one, and number two, we do it so much more efficiently than all other animals. And so yeah, it really is our kind of amazing evolutionary superpower. And if you know what evolution could have bequeathed us like we could be cooling down from pee, when you know that, sweat is so much less gross.

Brett McKay: Right, yeah, I’m grateful I don’t have to pee on myself to cool myself down. So let’s talk a little bit more about sweat. So some of the research that has been going on is trying to figure out how soon does the water we consume become sweat, and I think that also we need to ask too is like, how often are we sweating? Are we sweating all the time, or do we only sweat when we reach to a certain temperature? 

Sarah Everts: Right, we are sweating all the time, if we weren’t, we would be freaking miserable. Our body is constantly making micro-adjustments. And most of the time when we notice sweat it’s because we’ve upped our activity, and so our sweat glands are on hyper-drive and they’re like, “Crap, we gotta get going.” But at any moment, your body is releasing a tiny amount of sweat to make micro-adjustments to your internal temperature, and so as a result, we do need to drink water to stay hydrated. And there’s this awesome scientist that you’re kind of referring to, this guy named Michael Zech, who really likes going to the sauna, and one time he was like in the sauna, getting philosophical with his buddy, and they were like, “I wonder how quickly when you drink a glass of water, how quickly does that water get absorbed by your intestinal track, get, put into your blood, get dispatched to your internal organs, percolate to your skin, and then emerge out in sweat.” And when most of us get philosophical in the sauna, that’s the end of that. But because he’s a scientist, he could do the experiment. And so he spiked his favorite rehydration drink, which in Germany for him is this weird combination, 50-50 cola, 50-50 wheat beer. It’s kind of like a brown Shandy, and, so he spiked it with this chemical that he could measure and that’s not normally found in our bodies or in our sweat.

Sarah Everts: So he drinks his Colaweizen, it’s what it’s called, and then quickly undresses, gets into the sauna and starts measuring and capturing the sweat coming out of his skin at timed intervals. And he found that it took 15 minutes for that chemical tracer that he had put in his drink to come out of his sweat pores, which is pretty fast, right? 

Brett McKay: It is really fast. I didn’t think it would be that fast.

Sarah Everts: No, neither did I. He made me guess, and I guessed closer to an hour, but, yeah, no, it’s really fast.

Brett McKay: So sweat is primarily to regulate our body temperature, but we also sweat when we’re anxious or nervous. Why do we do that? 

Sarah Everts: That’s super interesting to me. So there’s a lot of speculation about this, one idea that researchers have is that it’s kind of anticipatory. When we’re anxious for most of human history, we’ve had to run really fast away from the thing that we’re scared of, and so it might be our body effectively predicting from anxiety that we’re going to be running and thus turning up the heat and that it would be wise to perhaps start the cool down strategy pronto. But it’s also this really interesting kind of vestigial aspect of evolution, so remember how I said humans have these salty sweat glands over our whole body, we’ve got millions of them. And what’s really interesting is that all mammals have those salty sweat glands, but they’re only located for most mammals in their paws. And that was because initially this eccrine sweat, this kind of salty watery parts of blood was used for grip, for climbing, and effectively when an animal got scared and had to like run away, possibly up a tree, that’s a little bit of that sweat would come out to help them with grip. And so when you’re stressed out and notice that your hands are getting sweaty, it’s a vestigial response from your mammalian predecessors that had to climb a tree in their anxious moments.

Brett McKay: Interesting. Another thing you highlight too is, sweat works better in certain climates than others in keeping us cool, so the whole cooling mechanism is evaporation. How does climate affect how effective that evaporation cooling is? 

Sarah Everts: Yeah, so in a hot climate, you can imagine the sweat is evaporated much more quickly away, and that’s due to some chemistry that you may have learned in high school, like in a very humid place, there’s already a lot of evaporated water in the atmosphere, and it’s kind of… Giving a push back to the water on your skin that’s trying to evaporate, to whisk away heat. And so in a desert, the water that you emit with sweat really evaporates quickly, and so that’s really good for cooling, it’s not good for hydration, that’s why in many very dry climates, you’re advised to wear cool, loose clothing, so that you kind of keep a little bit of humidity at your skin surface, right? But in really super sweaty climates or humid climates, sorry, you wanna take off as much clothing as possible to effectively give all those water molecules on your skin a chance to get out in a way, even when there’s already a lot of water molecules around in the atmosphere kinda taking up space.

Brett McKay: Alright, that’s a good practical takeaway there, keeping cool. I live in Oklahoma, it’s really humid here, so wearing lots of loose clothing during the summer, not probably a good idea, but if I were in Arizona, yes.

Sarah Everts: Yeah, exactly. And if you think about what a dog does while they’re panting, the whole reason that they’re heaving in and out, like the panting part, is they are trying to push all that water that is just evaporated up off their tongue and is making the surface just above their tongue dense with water molecules, they’re heaving all that wet air away and allowing dryer air to come on top of their tongue to make more room for more water molecules, so that’s the whole point of panting, is to kind of move that wet air away as fast as possible. Especially since they don’t have a lot of surface area for this cooling strategy.

Brett McKay: Well, let’s talk about how sweating differs across populations. So you… You started this book because you thought, “Well, I probably sweat more than most people,” and you just told me you have three million sweat pores. What influences how much we sweat? Is it primarily genetics or can our environment also play a role? 

Sarah Everts: Yeah, it’s a bit of a nature and nurture situation, so certainly some families are sweatier than others. And that could be due to just the number of sweat pores that you have on your body, there’s quite a range, also like the flux out of your sweat glands, so how quickly the sweat is coming out, that’s a big range. And your genetics might mean that you have a bigger flow than I do, or I probably have a bigger flow than you. And then there’s also you know how quickly how responsive your body is to temperature changes, but what’s really interesting is this nurture side, and evolutionary biologists are really digging into this right now, because when you’re born, you’re born with all the sweat glands that you’re gonna have, like sweat glands are developed in utero, but they don’t all become active at birth, it’s only in your toddler years that they come to… Become fully operational, so to speak. And so in those first early years of your life, your body is cluing into the environment in which you live and learning whether you’re in a super hot place, and so you have to maybe be a bit more active or more efficient, or whether you’re in a cool place. And so yeah, there’s this mix of both what you have genetically and where you spend your early years. I mean, the take a message though, is that you can blame your parents for both because they’re responsible for your genetics and also presumably where you spent your toddler years.

Brett McKay: Well, let’s say someone is born in a cool, cold, dry area and then they move to Florida, for example. Will their body adapt and sweat more or less based on that move? 

Sarah Everts: Right. So their… Your body’s acclimatized. So you know… But they do it a little bit slowly. And then you have this baseline, which you start with, so for example, right now, athletes are prepping for Tokyo where it’s super humid and super hot, some say it might be the hottest Olympics ever. And so they are all training in extremely hot weather so that their bodies can figure out how to be efficient at cooling in extremely humid hot weather. So you do… There is this process where your body does learn to adapt, but at some point we all have a baseline and that baseline is set in your toddler years. And so, yeah, you know there are some micro-adjustments, but at some point you’re stuck with what you have.

Brett McKay: We’re gonna take a quick break for a word from our sponsors. And now back to the show. Something I’ve read, I don’t know where I read it, maybe on the interwebs or on a men’s health magazine from 1992 or something, [chuckle] is that the fitter you are, the more you sweat, is there anything to that? 

Sarah Everts: Well, yeah, because if you are super fit, your body has learned that when you start exercising, when you start dialing up the temperature, you are not gonna be doing this for 30 seconds or even 15 minutes, you’re probably gonna be doing this for over an hour. And so athletes actually have a tendency to sweat more, the more that they train and the fitter that they are, and this is also true for people who have sauna going as a hobby. So for example, I noticed that when I moved to Germany and wanted to integrate with the locals who are all obsessed with going to the sauna, that my sweating rates got faster and more voluminous because I was suddenly going to the sauna and not just for a one-time deal, but going regularly and spending a heck of a lot of time in a really hot space. So ultimately it’s all part of this acclimatization process where your body is learning about your behavior and figures out that, “Oh, geez, when the temperature rises, she’s gonna be in there, or he’s gonna be in there for a heck of a long time, let’s get cracking on the cool down directive.”

Brett McKay: Are there differences between men and women in how they sweat? 

Sarah Everts: Not really. So generally, any differences that you see are most likely just due to volume to surface area issues, there’s not anything really biologically different in how sweat glands work or how many there are, but because men are on average larger than women, they’ve got slightly more sweaty activity because they’ve got that much more body to keep cool.

Brett McKay: Well, let’s get to the fun stuff here, which is like why sweat smells and the social aspect of being smelly humans. So you mentioned earlier that one type of sweat, I forgot the name of the gland, the sweat pore that produces… It starts with an A, right? 

Sarah Everts: Oh, apocrine.

Brett McKay: Yeah, the apocrine sweat, that’s the stuff so the bacteria on our skin in our armpits starts eating that stuff, and the bacteria fart, and that’s basically our BO. Why do, I guess I would say, I think Americans or westerns in general, why do we find BO so off-putting? Why don’t we like it? 

Sarah Everts: Well, so I would say two things. I think that Americans take it to a whole another level of insecurity, but I would say that for much of human history, people have been worried about the odor of themselves. So one of my favorite quotes, which is on my wall right now, it’s advice from the Roman poet Catullus, so this is like 2000 years ago, to his friend and then his nemesis, this guy named Rufus. He says, “Wonder not, Rufus, why none of the opposite sex wishes to place her dainty thighs beneath you, not even if you undermine her virtue with gifts of choice silk or the enticement of a pellucid gem. You are being hurt by an ugly rumour which asserts that beneath your armpits dwells a ferocious goat. This they fear, and no wonder; for it’s a right rank beast that no pretty girl will go to bed with. So either get rid of this painful affront to the nostrils or cease to wonder why the ladies flee.”

 So, I love that because it speaks to the fact that for at least 2000 years, we’ve been a bit worried about our body odor, but most of that time, the way that we’ve dealt with it is to wash with water, possibly soap and/or apply a huge amount of perfume to overwhelm our BO. And it wasn’t really until the turn of the 20th century when what we use now, deodorants and antiperspirants get invented. And so up until this point, people have a background body odor of each other, they know each other’s body odor really, really well, and it reminds me of the difference between smoking laws. Back in the day, you’d go to a bar and there would be tons of smoke and you’d go home and you wouldn’t notice it. And now, because we have made this very smoke-free environment, when you do go to a very smoky place, you notice it so much more, it feels so much more intense.

So over the 20th century, we dialed down our body odor to those around us a lot more because of these products, but simultaneously, those that marketed these products use this thing, invented this thing called whisper copy, which puts the fear of stink in humans and in the 1919s they started their advertising strategies towards women, and they started trying to convince women to buy deodorants and antiperspirants by saying, “Listen, if you sweat, you stink and people are talking about you behind your back, and not only is this gossip hurting your reputation, but it’s gonna completely negate your ability to find a man.” It’s the 1919…

Brett McKay: You’re gonna be an old maid.

Sarah Everts: You’re gonna be an old maid, and eventually by the 1930s, when they’ve got the fear of stink in so many women that they’ve maxed out the market share and they’re like, “Oh, no, we still wanna make more money,” they’re like, “What should we do?” “Oh, dudes smell too.” [chuckle] But by this time, they’ve spent a couple of decades presenting this, presenting deodorants and antiperspirants as a feminine product. And so, they have to dial up the masculinity in their advertising strategies, and so they put deodorants and antiperspirants into the manliest things they can imagine, which in that case, at that time was like a whiskey jar, [chuckle] so they’re selling deodorants out of whiskey jugs. But also their tactics still rely on this thing called whisper copy, putting social fears of exclusion in men, but instead of focusing on romantic exclusion, they initially tell men ’cause it’s the ’30s, the Depression, that they’re gonna lose their job or they’re not gonna get a promotion, that effectively stinking in the board room is going to hurt your career. And nowadays, you see… [chuckle]

Both of these strategies, fear of social exclusion at work or in love being applied to everybody equally. But yeah, it’s that whisper copy, this fear and you see this a lot in North America.

Brett McKay: Let’s talk about the smell of BO. So the quote you listed, the guy described it smelled like a goat. How do scientists… I mean, you just… There’s people who they smell armpits for a living to try to figure out what is this smell.

Sarah Everts: Yes.

Brett McKay: How do they describe the smell of BO. So I’ve always think it’s like, it smells like a onion Whopper burger. What’s the scientific description of it? [laughter]

Sarah Everts: I have not heard that, and I love it. But yes, so when scientists sniff armpits, they actually… Chemists actually measure the molecules coming off of an armpit, and they have actually found what’s known as two top notes. And one smells kind of goaty, kind of like feedy goaty smell, and the other one smells like overweight, kind of like tropical fruit with a touch of onion. So your onion Whopper burger is not like totally off. And so these two top notes are the reason that when you go into an elevator and you’re like, “Whoa, there was a really stinky person here before me.” You know that it was a human instead of, say, a stinky dog or a stinky horse. And those two top notes are the things that dominate our body odor, even though there’re actually hundreds of other odorous molecules that kind of add to our symphony of smell. And it’s the kind of relative proportions that give you your own odor print that is distinguishable from my odor print at least to a dog who’s, say tracking you versus tracking me.

Brett McKay: Are some people smellier than others? 

Sarah Everts:Yeah. [chuckle]

Brett McKay: Alright. And is that just genetics? 

Sarah Everts:You know it’s due to… You know the bacteria that you produce or not produce it, but that you recruit into your armpits. So we know about our human microbiome. We’ve got trillions of bacteria in our inside or digestive tract, but also all over our skin. And for the most part, this bacteria is acting as a really helpful defense against pathogens, but also in our armpits, that particular ecosystem attracts what’s known as Corynebacteria as well as Staphylococcus and a whole bunch of others, but people who have a higher proportion of Corynebacteria in their armpits often have a more potent pong.

Brett McKay: And the crazy thing is… The crazy story I read in the book that really startled me was the guy who wasn’t really smelly, but then he was amorous with a woman, and then after that, he just smelled, he had a BO problem and he kinda did, he did some amateur scientific stuff and figured out, I think I got some of her bacteria on me now. I’m now, I’m a smelly guy.

Sarah Everts: Yeah, well, he turned it into a PhD project [chuckle] and effectively was super interested. This is like in the early days of microbiome research, and although we’ve known for a long time that the actual source of our odor is the byproducts from these microbes. He thought, okay, well, there’s this idea of probiotics like, can you introduce good bacteria and could I possibly re-introduce my good bacteria because… Yeah, he had this experience where after an amorous trust, his whole body odor changed dramatically. And it was quite alarming for him, and ultimately he managed to re-populate his own body with his own bacteria, ’cause he’s now in the process of his PhD, like analyzing exactly, the microbial membership of his armpit. He has those skills, and he ended up having this t-shirt that he had used for years to paint when he had to paint a room in a house, and it had, I guess, the bacterial populations of his pre-amorous trust self. And so when he put it on to paint in a house, he noticed after that that he had managed to turn his body odor back to normal for him.

Brett McKay: So this guy, not a stinky, the lady that he slept with stinky, but generally, are there differences between the smell, the BO smell of men and women? 

Sarah Everts: So not a heck of a lot, but there are some studies that have shown that of these two top notes that I was talking about, that men have a higher proportion of the stinky goaty odor and that women have a higher proportion of the tropical fruit overripe oniony odor. But quite honestly, everybody produces both of these things in their armpits, but yeah, it’s slightly proportionally higher for women to produce the oniony odor and men, the goaty one.

Brett McKay: Well, let’s get to why you went to Moscow, you went to a basically it was a smelling dating thing. Recently people were getting sweat and you were getting matched with another person based on your sweat, and I think people heard this idea of pheromones, where you buy cologne with pheromones and some sort of like Love Potion and people will be attracted to you.

Sarah Everts: Oh my God, we have to talk about that after. [chuckle]

Brett McKay: Alright. Well, is there anything to this idea that there are pheromones in our sweat and being exuded by our body odor that makes us attractive to other people? 

Sarah Everts: Well, because a good chunk of our body odor appears in the sweat glands that produce sweat that show up at puberty and puberty is when we become sexually mature. People think or people suspect that there’s gotta be some sort of role that our body odor plays in mating. And so people have spent decades trying to track down a human pheromone of our armpits, and they’ve gotten a lot of really tantalizing clues, like I think a lot of people have heard of this one experiment, where women were given t-shirt samples worn by men and the women found the men to be most attractive when their immune systems were different enough that should they procreate, their progeny would have a super strong immune system, and if you think about that, it makes evolutionary sense because, you know…

 For a lot of human history, our major foe has been microbial; plagues, infections, things like that. And so, it behooves us if you’re gonna mate, to mate with somebody who’s gonna give your progeny a chance at survival by having a great immune system. But even though you can do these experiments by asking women to pick the odor that they like and analyzing the blood of everybody and being like, yes, this would be a good immune match, in terms of plucking out of our body odor, a molecule that is known as a human pheromone, that’s eluded chemists.

And actually, when you know about what a sex pheromone in the animal kingdom does, it is probably a good thing. So for example, a bombykol is this pheromone that moths make, and when a female releases bombykol, literally every male in the vicinity makes a beeline towards her. It is like the scientific definition of a booty call. Or wild pigs, so when male wild pig breathes heavily on a female in heat, a set of pheromones called androstenol and androstenone, that is in his saliva and percolates up in his heavy breathing. When she sniffs that, she immediately turns around and lifts her rump in the universal sign that it’s time to start a family.

So, that kind of instant reaction is a little bit alarming, but if you think about the human world, it’s just as well, we haven’t actually isolated a human sex pheromone because that could be a little dire, and that hasn’t stopped online entrepreneurs from selling pseudo-science potions that they call human pheromone colognes that sound scientific, and typically include androstenol and androstenone. So these are those wild pig pheromones, and they are found in the armpits of humans, but both men and women produce them equally, so it can’t be a pheromone, it can’t be a message from one, for example, biological sex to another. But if you wear one of those pheromone colognes, you just might attract a female, but it’s going to be a female wild pig rather than a female human. And no judgment if that’s your goal, but yeah, it’s probably not what most of the people buying those things want.

 But in terms of romance, this kind of notion of a human pheromone people say, “Oh, yeah, I fell in love with him or her because of the way that they smelt, about their unique odor print as opposed to what we know from the strict definition of a sex pheromone, which would work equally on literally every member of the human species; it’s anonymous, it’s not unique, it’s not the thing that made you fall for whoever you fell for as your one and only.

Brett McKay: Okay, so basically the scientist, there’s something going on because people can detect differences, and I think it was another study too, men find the smell of women ovulating more attractive than women who aren’t. Was there a study like that with T-Shirts? 

Sarah Everts: Yes.

Brett McKay: Yeah.

Sarah Everts: Yeah, lap dancers.

Brett McKay: Yeah, lap dancers got more tips. They suspect there’s some kind of odor going. So like scientists, there’s something going on but they just don’t know what basically is what’s going on.

Sarah Everts:Yeah, that is pretty much basically what is going on and there are so many molecules percolating out of armpits that yeah, it’s been a long, hard road, and many researchers have really tried to pluck out something that’s giving us a strict cue that I want to mate with you, and that so far has been unsuccessful.

Brett McKay: Well, another thing that can get transmitted via our body odor is fear. Have you figured out what fear smells like? 

Sarah Everts: That’s a super interesting area of research, it stems from the fact that a lot of law enforcement folks say that when a person comes in for questioning, for interrogation, that they come in smelling like themselves, but after interrogation, after all those tough questions have been asked, everybody leaves smelling the same of this strong, potent anxiety odor, and when researchers have tried to follow up on that anecdote, again, they found really interesting evidence that this is true, so they gave people tight white T-shirts to wear and put them in front of a television and had them watch a nature documentary, and then had them watch a really scary movie, so that they produced just their normal pong and then super stressed out, scared body odor. And when they presented those T-shirts to a panel of sniffers, the sniffers could distinguish from perfect strangers who was stressed out and who was just stinky, who was actually fearful than who was just smelling.

 The folks with probably the most interest in this is the military, because you can imagine if you have a bunch of soldiers in a tank and one starts getting really scared that this odor is gonna be detected by others, and it might spread fear when all of these soldiers really need to stay focused and hopefully a little bit unafraid. And so, the military is interested in plucking out this anxiety odor molecule so that they can effectively capture it, like you would capture a poison gas. And there’s other kind of more dystopian applications that you can imagine. If you figured out what that odor is, the one that is like the smell of fear, you could use it on crowds to do crowd control. So, again, chemists have been trying for a long time to pluck out that molecule, they haven’t so far been successful, but they are quite close.

Brett McKay: Well, let’s talk about deodorant and antiperspirants a bit, circle back to that. It became a thing in America at the turn of the 20th century, they’re using that Whisper copy saying you’ll be an old maid or a bum if you don’t use deodorant, but there’s a difference between deodorant and antiperspirants, what is the difference? And let’s talk about antiperspirants ’cause I’ve been hearing a lot about that, that antiperspirants are bad for you and you should use a natural deodorant. What does the research say about that? 

Sarah Everts: Sure. The main difference between deodorants and antiperspirants is how they work to thwart sweat. Deodorants have antiseptics in them, and so effectively what happens is, you put on deodorant and you kill all the bacteria in your armpit, including the ones that cause odor.

Whereas antiperspirants plug your sweat pores in your armpit, which include both the apocrine, the ones making that waxy sweat that bacteria like to eat, and also just the wet stuff that comes out when you’re exercising. And so, antiperspirants work by literally cutting off the food supply to the hungry bacteria and in doing so, prevent odor from being formed. And that’s why antiperspirants though also help you avoid wet patches, whereas deodorants are just dealing with odor. And the way that antiperspirants plug pores and have always plugged pores literally the very first antiperspirant products relied on aluminum salts, so it used to be aluminum chloride, now it’s a more complicated aluminum salt. But there’s a lot of people who have fears about putting on a product that’s got aluminum in it in part because aluminum in high amounts is a neurotoxin.

 That being said, in terms of our Earth, we have evolved on a planet where aluminum is one of the highest percentage metals in the mantle, and a lot of the food, for example, that we eat like sesame seeds, even potatoes have high amounts of aluminum in them, and so our body has evolved ways to rid itself of aluminum, and that’s usually through the kidney, which filters out nasty stuff, not just aluminum from our blood and dispatches it out in pee. And so, because of these concerns about aluminum being a neurotoxin, it is a neurotoxin, there’s been worries that if you put on deodorants that you’re going to up your body burden so much that it will give you neurological problems or Alzheimer’s. All the research has been done on this for decades and shows that there’s really not a strong correlation at all between wearing antiperspirants and Alzheimer’s, it’s not something to fear, yet it keeps coming back.

 And actually, the European Commission has a scientific committee that looks at consumer products, and they recently revisited the issue and forced the cosmetic care industry to do some pretty sophisticated experiments to see whether putting on antiperspirant effectively gets aluminum into your bodies at a level that is dangerous, and they found that there was no cause for concern. Those studies were published in 2020, so yeah, aluminum is not great to ingest but we are getting it in our bodies from eating and from all sorts of other things like lipstick and other things have have aluminum in it. But yeah, it’s probably by wearing antiperspirant everyday, it’s probably not pushing that aluminum body burden to the point of concern.

 That being said, I mix and match. When I have to, for example, stand up in front of a whole bunch of people and I don’t wanna have sweaty patches ’cause I’m nervous, I’ll sometimes wear antiperspirant, and if it’s a day where I don’t have to do anything particularly huge, but I don’t feel like smelling my own BO, I’ll put on deodorant. I don’t think it’s a huge cause for concern, but yeah, it has been one for many years.

Brett McKay: So we sweat to keep cool and it’s an automatic process, you have no control, whether you sweat or not, but cultures around the world and across time, they’ve come with practices where they can basically create an environment where they purposely sweat. So I’m talking saunas, sweat lodges, Asian cultures have similar hot being really hot. Why do you think this is a universal across humanity where we just wanna sweat? What is it about getting really hot and sweaty that feels good? 

Sarah Everts: Yeah, we create that catharsis and I think part of it is that when you work up a sweat, you effectively even, say you go into a sauna or a jjimjilbang in Korea or a hammam in the Middle East, you are effectively forcing your heart into a little tiny workout because you go into this really hot room, and in order to cool down, your heart starts beating fast to move the hot blood in your interior out to the surface of your skin so that it can be cooled down by sweat evaporation, so you effectively get your heart pumping. And that has knocked down effects where you produce those same happy hormones that you get when you exercise profusely or go for a run, the runner’s high, the endorphins. You also have epinephrine that’s being produced, and so you do actually get a biochemical high when you sweat profusely in a sauna. So I think that there is this feelings of joy and catharsis that you get when you sweat in a sauna, and also that you get if you really work out hard and have that euphoria, that post-workout euphoria.

Brett McKay: Something you didn’t mention, it doesn’t detox.

Sarah Everts: Oh, yes. That is the biggest myth ’cause yeah, if you ask me what is my biggest sweat pet peeve, it’s this notion that sweating is a way to detox, and that’s so totally wrong, and it reveals a fundamental misunderstanding of how our bodies work. Remember how I said that sweat is sourced from the watery parts of blood? 

Brett McKay: Yeah.

Sarah Everts: If you were to detox by sweating, where a detox… The idea of a detox is like you get all the crap that’s circulating around your body out of your body. So if you were to detox by sweating, you would literally have to get rid of all the liquidy parts of your blood, you would have to sweat out all your wet parts of blood. You would have to effectively dehydrate yourself, at which point you would dry up and die. That just doesn’t make sense. Instead, our bodies detox using the kidney. Our kidney filters out all the gunk in our blood and dispatches out all the bad stuff in pee, and anything that’s coming out in sweat is just incidental. So yes, certainly, you can sweat out some nasty things that are circulating in your blood if they happen to be there, but also you’re sweating out glucose, which your body uses as energy and hormones, anything that’s in that liquidy part of blood. And so, this notion that sweat is a detox strategy, super, super wrong. And it’s really good that we don’t detox by sweating because yeah, you don’t really wanna dehydrate and die.

Brett McKay: Okay, so yes, sweating does remove stuff from your body, but that’s just incidental, you’re not gonna be able to purify yourself with just sweating. So when you go to the sauna, just enjoy the sauna, simply because it feels really good to get hot and sweaty, enjoy that little workout, you get in there, the endorphins, just do it for this joy of sweat itself.

Sarah Everts: Exactly.

Brett McKay: Well, Sarah, this has been a great conversation. Where can people go and learn more about the book and your work? 

Sarah Everts: They can go to my publisher’s website, Norton, or my own website,, or they can grab the book off a shelf and read it.

Brett McKay: Well, Sarah Everts, thanks for your time. It’s been a pleasure.

Sarah Everts: Thank you so much.

Brett McKay: My guest today was Sarah Everts. She’s the author of the book, The Joy of Sweat, it’s available on and bookstores everywhere. Check out our show notes at where you can find links to resources where you can delve deeper into this topic.


Well, that wraps up another edition of the AOM Podcast. Check out our website at, where you can find our podcast archive as well as thousands of articles written over the years about pretty much anything you can think of. And if you’d like to enjoy ad-free episodes of the AOM Podcast, you can do so on Stitcher Premium. Head over to to sign up, use code MANLINESS at checkout for a free month trial. Once you’re signed up, download the Stitcher app on Android or iOS and you can start enjoying ad-free episodes of the AOM Podcast. And if you haven’t done so already, I’d appreciate if you take one minute to give us a review on Apple Podcast or Stitcher, that helps out a lot. And if you’ve done that, thank you. Please consider sharing the show with a friend or family member who you think will get something out of it. As always, thank you for the continued support. Until next time, this is Brett McKay reminding you to not only listen to the AOM podcast, but put what you’ve heard into action.

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