Why do we smell (and how concerned should we be about it)?
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Fresh for everyone. This is a CBC Podcast. Hi, I'm Dr. Brian Goldman. Welcome to The Dose. Maybe I watch too much cable TV, but I'm seeing lots of ads to deodorize pits and privates. North Americans spend billions of dollars per year to smell good. What to make of our modern aversion to the stinky parts of our bodies?

So this week we're asking why do we smell and how concerned should we be about it? Hi Sarah, welcome to The Dose. Hi Brian, how's it going? It's going well and of course I did apply my deodorant today and you know I do watch a lot of cable and there's drug ads and there's a whole lot of body deodorant commercials and having written a book on the subject, do you kind of cone in on those commercials too? Oh I'm totally obsessed with them. I hate them.

I mean, from like the earliest commercials for a product called Odor, oh no, to yeah, the new all body deodorant BS. Yep, I'm obsessed. Which is why we want to come to you for all the answers because, you know, quite frankly, there's a medicalization of it, but not many of my doctor colleagues know a whole lot about body odor other than the fact that it exists. And I want to get some of the answers from you. But before we begin, can you give us a hi, my name is, tell us what you do and where you do it.

Hi, my name is Sarah Everts, and I am a science journalist and also a journalism prof at Carleton University. And I wrote a book called The Joy of Sweat, The Strange Science of Perspiration. The Joy of Sweat, you know, that is the perfect title for a book on the subject. And it also tells me that you have a sense of humor and you're not going to sweat it.

When we have this conversation, I'm sorry, I could not resist that. So let's start with the basics. How do you define body odor? Well, I think we all have BO and it's actually kind of different depending on where you're sniffing on your body. But every single person has about 100 or two volatiles. Those are like small molecules that are floating up off your body that make you smell the way you do and me the way I do.

And there are some top notes that scientists have found, ways that you can tell when you go into an elevator that it was a stinky person who was there before versus a stinky dog or horse. But besides those top odors that usually come from our armpits,

We also have a symphony of other more delicate smells that allow our friends and family to identify us or to even notice that we're anxious. You know, when you said top notes, the first thing I thought of was red wine, like uncorking a bottle of red wine and let's get the top notes on the... But that is not what you are talking about. You have already brought a lot of layers to this conversation. You've mentioned volatiles, they're chemicals,

that are produced by bacteria that are on the human body. And they have names, don't they? Yeah, yeah. So the two top notes for humans are trans-3-methyl-2-hexanoic acid. And that is a kind of a goatee odor that usually you associate with locker rooms.

And then we also have 3-methyl-2-sulfonylhexanol. And that's like, imagine raw onions meets slightly rotting passion fruit or, you know, tropical fruit. It's kind of like oniony and it's kind of like also too sweet. And those are two odors that kind of really identify humans from other animals. But again, we have like...

hundreds of molecules that are coming off our body, you know, it's off our neck, off our armpits. And most of those molecules are actually made by our skin microbiome. So the bacteria living in concert with us that, you know, protect us from all sorts of, you know, you know, pathogens that are trying to attack us and trying to get in through our skin. So, I mean, the good news is your BO is not you. The bad news is it's, you know, bacteria, you know,

eating your sweat, eating your, you know, your skin fluids and effectively farting out your BO. Is there much of a difference between the armpits and the private areas, you know, the genital areas when it comes to bacteria and when it comes to the typical odors? Oh, absolutely. So because it's your microbiome that is eating your sweat,

and metabolizing it and turning that into the odor that you give off to the world. The actual symphony of smell is really dependent on what's living where. And the microbiome of your armpit is different from the microbiome of your shoulder. Even researchers have found that the microbiome of one finger is different from the other. And so there are some kind of primary culprits, bacteria that really like to live in our armpits.

and are responsible for at least that first top note, the goatee one, and that's Corinna bacteria. And our armpits are kind of moist, wet ecosystems versus, you know, our elbow, which is dry. And so, yeah, the BO that's coming from your feet or your genitals or your armpits or your neck is

or at the top of your head are all slightly different based on the microbiome living there. That being said, the reason that your armpits in particular get particularly smelly

in your teenage years is because a special kind of sweat gland gets activated at adolescence. And anywhere where hair grows in adolescence, this apocrine gland also starts to grow and it releases a waxy fluid. So that waxy fluid's a lot more like earwax than the salty wet floods that we associate with

cooling down. So you have these two kinds of sweat glands. The kinds that get activated in adolescence, those are the ones that make some of the more potent odors that people try to mask. This is an interesting question. Adults are not just socialized, but we love our children. We take care of them.

Does that have anything to do with the fact that babies and young kids don't smell because they haven't reached puberty and they're more likely to smell sweet? Is there an evolutionary reason why all of this gets triggered by puberty? Right. Oh, gosh. There's about 20 different ways I could answer that question. The first thing I'd say is that I do think babies and small children smell, in fact,

they smell so good. A lot of people, I have a friend who actually doesn't want any children her own, but goes around and finds friends who have just had babies just so that she can sniff their heads. I do think that like people do like the smell of newborn kids, but you're right. It's not that ripe rank odor that comes from the armpit.

So evolutionarily, that apricot gland that exists in our armpit is a lot similar to the glands that mammals use to release odors that are involved in chemical signaling like pheromones. And so there's a lot of speculation that the reason we get particularly smelly at puberty, which is when we become sexually mature, capable of having pheromones,

kids is that it has something to do with partnering up. And there's a lot of really interesting research in that area, but there's also a lot of really interesting research just looking at what we learn from each other based on other smells. So we can identify our siblings and our children, even if we haven't seen them for a long time, especially siblings who are not hung out for years.

We can tell when perfect strangers are anxious. And, you know, there's also some really interesting new evidence that we can sniff out when somebody's immune system is activated and we find that repellent. And so evolutionarily, that would make sense that you would want to not hang out with somebody who's fighting an infectious disease because that could also lead to you getting maybe infected.

But it's complicated because, of course, we also really love the people close to us. We also love their smell often. And so, you know, there's a lot of competing issues with, you know, our odor and its connection to memory and emotion, but also the fact that we've become, you know, really visual people, a visual species. And so, you know, it's not just smell that's motivating our behavior.

It sounds like there's a lot of odor processing going on in the brain. Is this happening primarily in the primitive parts of our brain? It's happening in the olfactory bulb. So right, you know, right at the edge of the nose. And then there's like processing all over.

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Fresh for everyone. In the fall of 2001, while Americans were still grappling with the horror of September 11th, envelopes started showing up at media outlets and government buildings filled with a white, lethal powder. Anthrax. But what's strange is if you ask people now what happened with that story, almost no one knows. It's like the whole thing just disappeared. Who mailed those letters? Do you know?

From Wolf Entertainment, USG Audio, and CBC Podcasts, this is Aftermath, the hunt for the anthrax killer. Available now. What do we know about how odor attracts or repels us from potential romantic partners? Oh, this is one of my favorite studies. And it was done in the 90s by a guy named Klaus Vedekin. And he gave a bunch of t-shirts to men to wear and got a lot of women to sniff them. And I'd like to like...

point out that most of the research in human chemical signaling or pheromone communication is done in straight cis people that doesn't reflect the greater gender and sexual diversity that actually exists in humanity. But

These women were given the T-shirts that these men got to wear over the course of multiple hours and sweat into. And what was interesting is they preferred the odor of men whose genetic complement, their genes complemented the woman's genes so that their progeny, if they managed to mate, would have a very strong immune system.

So the way that they know this is that they took everybody's blood at the same time as enrolling them in the study.

And, you know, what's interesting about that is it kind of makes sense. If I am going to pick a mate evolutionarily, I want to pick one that if we have a child, that child's going to be really robust against the major challenges. And, you know, if you think about human evolutionary history, plagues, pandemics, infections, these are the things that, you know, kill us when we're young and when we're old. So having a strong immune system makes a lot of sense.

With body odor, it's more like a deal breaker rather than the thing that like is a make or break situation. Do you know what I mean? I also wanted to point out that it's not all about sex. Like there's been lots of really interesting studies that have shown that people choose friends based on BO, that like people who are BFFs and had a really strong friendship relationship.

right off the bat, have a similar odor profile, more similar than your average person on the street. So we are maybe a little narcissistic. We like smelling people who smell like us. And so there is this in-group...

And I would also point out, though, that that smells like us thing has been used in really terrible ways, too. Right. People are xenophobic and have made all sorts of xenophobic statements about, you know, people who smell like.

garlic or cabbage or curry. And, you know, this sort of like smells different has been used in really awful racist ways. Did human beings always have a latent fear of smelling bad that just got unlocked by a marketing campaign? Or did the marketing campaign put the idea in our heads that we should fear smelling bad?

I think humans have always wanted to optimize their smell. There's lots of evidence that through time, people were using perfumes in particular and soap and water to improve their BO. But I think what happened at the turn of the 20th century and with these marketing campaigns was a supersizing of that fear and also connecting it to a very specific new product that

and saying, okay, so you've done soap and water and perfume, but have you done deodorants and antiperspirants? And if you don't get on this bandwagon, you're going to be left behind.

And then I think also, you know, in the 20th century and even now and why I think that there's been this spike in whole body deodorant, which I think is terrible for both biological and cultural reasons. But in terms of the culture side of things, effectively during the pandemic, right, we got used to curating our food.

online persona so that we can, you know, make ourselves look great on Zoom or Teams or whatever video platform. And then, you know, suddenly everything opened up again and we realized, oh no, we're

We have to exist in the world. And the thing with sweat and body odor is that when it happens, it happens. If you think about things that embarrass humans that are stinky, like maybe a fart or a burp or something like that, you have usually enough time and advance warning from your body that you can go into a bathroom or to the corner to deal with the situation. But when your body gets to open the floodgates,

message, that just happens. And you have absolutely no control over your sweat and your consequent odor if you haven't applied product. And so I think that this is partly why in a post-pandemic world, we're also seeing kind of like another spike in anxiety about our BO because we really like to have curated online presence.

And our body sometimes doesn't go along with the plan. So someone else's body might give off a pungent odor, but mine does not. So that leads us quite naturally to the next question. What are the healthiest ways to get rid of body odor? Definitely don't apply deodorant to your whole body.

I think that it's kind of questionable to put on full body deodorant for several reasons, not the least of which deodorant is just an antiseptic. When you put it in your armpits, it kills the bacteria there that would make your strong BO and then it goes away, right? But if you were to apply full body deodorant to your whole body, that would be effectively applying antiseptic on all of your skin.

Right. Your skin has a microbiome that is most of the time working on your behalf to, like, keep you safe from pathogens. And so why would you try to effectively destroy their populations on your whole body?

It just doesn't make sense. And I think it's a bad idea. Putting it in one spot, your armpits for a small amount of time, fine, but everywhere. Also you smell like yourself and that's the odor that your friends and family have gotten to know. And at some point you have to just come to terms with the fact that you have an odor and that you actually smell

probably smell good to the people who love you. Are there chemicals that we should avoid in deodorants? A lot of people worry about aluminum. And aluminum is not usually in deodorants. Aluminum is in antiperspirant. And in fact, I'd say that effectively there is no product out there that can stop your sweat from happening that doesn't have aluminum in it.

That's because in order to plug your sweat pores, it needs to crystallize. And aluminum is just the only element that mixed with other chemicals allows that plug to happen. What's really interesting is that there's a lot of really terrible greenwashing out there about natural deodorants. It's called the crystal rock. And if you look at it, it's white and clear. And you see this everywhere. If you look at the back...

it effectively will have an aluminum potassium alum in it. So it is all aluminum, even though on the front, it usually says no aluminum chlorohydrate. And

and aluminum chlorohydrate is in the antiperspirants you'd get at a standard pharmacy. And so I guess the next question is, should we be worried about aluminum? There is clear evidence that aluminum is not great on your brain in high quantities, right? Like it's a neurotoxin. It's also one of the most common elements in the Earth's mantle. So we are consuming aluminum all

all the time. It's in spinach, it's in sesame, and our body is very good at getting rid of it through our kidneys. And so effectively, there's been a lot of studies that have looked at what is the safe level to consume aluminum through your mouth, like through products that you eat. But there's been like very little on the cosmetic care access. So like how it gets through your skin.

And this has led to some concerns that, oh no, what if we're getting too much aluminum through things like antiperspirants that's coming in through our skin as opposed to through our mouth?

It was of such concern to the Europeans that they launched a committee to ask for much more data on this. And so the cosmetic care industry got together and did some research. And effectively, the results of that is that, you know, if you're using antiperspirant a reasonable amount on in your armpits, there's really no concern about doing that for, you know, having aluminum too much in your body.

You've already mentioned that if you were to use a full body deodorant, you may be stripping down the bacteria that's actually good and healthy for us. Are there any other downsides of working too hard to get rid of body odor? Well,

Well, I would say that if you happen to use whole body antiperspirant, right, because you don't want to sweat at all, that is a terrible idea because you sweat like the other kind, the salty floods that evaporate heat and keep your body cool. That's necessary for avoiding death by heat stroke and for keeping your body at a reasonable temperature. So putting...

Yeah.

their knee. And so they put antiperspirant there. I mean, I don't think they're going to die of heat stroke by controlling the sweat in that one area, but sweating is good for you. Our evolutionary superpower, it's why we can run marathons. It's why we can cool down better than any other animal on this planet. So why you would try to restrict that on like a whole body level just strikes me as bananas.

And I guess the final question I'd ask you, just to put this in perspective, how much do we actually require deodorant? I guess that's in the nose of the beholder.

Oh, yeah. You know, some people are really into BO. I went to a smell dating event once to report on it where people intentionally sniff each other's BO because the idea is that at some point you're going to smell it in a partner. So you might as well use that as a triage, as your first swipe triage instead of, you

And so like some people are really into it. I do think that everybody needs to tone things down in North America here. We are very obsessed with giving off the impression that we have absolutely

no body odor whatsoever, which is, you know, just a fallacy. I lived in Germany for a while, had to go a lot to France, and there people are a little bit more relaxed about it.

You know, they are more keen on finding products that match their body odor. We're just going effectively as they are. I also think that a lot of this shaming exists in Western cultures. And, you know, deodorants and antiperspirants are not sold in all countries.

So I do think it's probably, you know, contingent on where you are, how much deodorant you want to put on. But I also think that everybody needs to, you know, chill, as my kid would say, chill about their BO. And, you know, everybody has a moment where things get through the cracks. And if that happens, it is what it is.

Whole new meaning to the phrase, things get through the cracks. Oh, no. Well, the puns could have come a lot faster and a lot and a lot sooner. But Sarah Everts, you have a very balanced perspective and you are a fountain of information on why we do smell. And I want to thank you for coming on the Dose to talk about it. It was my pleasure.

Sarah Everts is the author of The Joy of Sweat: The Strange Science of Perspiration and she's an associate professor and CTV chair in digital science journalism at Carleton University. Here's your dose of smart advice: body odour is primarily caused by apocrine sweat glands located in the armpits and genital regions that become activated during puberty. These glands secrete an oily fluid that is odourless.

Secretions only emit a scent when body heat causes bacteria in those regions to multiply and release smelly byproducts. Common skin bacteria that produce body odor include Carani bacterium, Staphylococcus, and Cutibacterium genera. The chemicals that generate odors are volatile organic compounds that include fatty acids and thioalcohols.

Body odour is also determined by other factors including genetics and diet. The chemical nature of body odour may change with age. For instance, the so-called nursing home smell of older people may be due to unsaturated aldehydes. Men have larger sweat glands and generally produce more sweat than women.

Some medical conditions can be diagnosed by odor, including malaria. As well, scientists have developed a body odor disgust scale, or BODs, that reflects perceived vulnerability to disease. Some antiperspirants contain aluminum chloride that reduces sweat by plugging sweat ducts. Others kill skin bacteria that produce the odor-causing chemicals.

There is no compelling reason to apply deodorant to the entire body. On the contrary, the bacteria on the skin serve as the first line of defense against germs and chemicals that might penetrate the skin and cause harm. Researchers are developing ways to reduce odor more permanently by introducing new bacteria into armpits and private areas, bacteria that don't cause odors. If you have topics you'd like discussed or questions answered, our email address is thedoseatcbc.ca.

If you liked this episode, please give us a rating and review wherever you listen. This edition of The Dose was produced by Brandi Weichle and Samir Chhabra. Our senior producer is Colleen Ross. The Dose wants you to be better informed about your health. If you're looking for medical advice, see your health care provider. I'm Dr. Brian Goldman. Until your next dose. For more CBC Podcasts, go to cbc.ca slash podcasts.