What your body odour says about you

13:25Katie Edwards:Well, in theory, yes, because if there is information here, we can miss it. I mean, and there are some interesting starting is saying, for instance, that we may be able to communicate our emotional state through body odors. And if you have perfume, it's likely that that will mask that cue or signal.

13:51Mats Olsson:Because I always think, you know, when you watch historical dramas on TV and, you know, they're getting really, really close and it's a love scene and they're kind of breathing all over each other and they're getting really close. And I always think they would stink. Yeah. I mean, I always think, really, would you really be getting that close to them? Yeah. So if we all stopped washing, for example, would we become nose blind to sense? because I'm just thinking that the other day, Matt, I went to a supermarket and it was quite full. And I followed around, unfortunately, this man who, I mean, he not, it was a stranger to a bar of soap, let's just say that.

14:34Mats Olsson:And it was dreadful. And I can't imagine ever smelling somebody from that distance and thinking, oh, delicious.

14:45Katie Edwards:us let's say that we move back like a few hundred years and maybe people then didn't wash as much and and then we would all in an absolute sense smell more so we would be able to smell each other and you could maybe feel who is sort of in the other room when you're getting through the door but it's reasonable that we would have then an acceptance for body odor it wouldn't be synonymous with, oh, this person has a bad hygiene or poor mental health or something. It will be natural. And my guess is that you would divide people into better smelling and worse smelling as you do with maybe when you classify people's sort of faces or body shapes or anything.

15:36Mats Olsson:So what kind of information does body odor carry about a person?

15:39Katie Edwards:It's an approach avoidance instrument. I like this. I like this person. That's sort of main message there. We don't have a language for odors. I mean, I could go to Italy and then I could call you and I could describe a vase with words so that you will see a vase for your inner eye that is very similar to the one I'm describing to you with words. But if I would find an interesting new odor that I really like, and I try to describe that to you, it would be impossible. There is no word for it, right? I could say maybe, I could say like, well, it smells like jasmine and cinnamon, and then you get a hang of it.

16:20Katie Edwards:But there is no language to describe the odor itself.

16:24Mats Olsson:So can you smell fear, Matt?

16:27Katie Edwards:Some studies actually indicate that. I mean, to start with, if you're really fearful, that could affect your bodily processes. Maybe you sweat more and you have sort of the stress system alarmed over a long time. That could probably put the new molecules into the bloodstream that comes up to the skin through sweat glands. But in the short run, is there like a cueing system or signaling system? And there are some studies indicating that emotions can actually be somehow communicated. And the typical experiment shows that if you have a person looking at the videos, that could be either happy or induce fear.

17:17Katie Edwards:And then you collect the body odor from these people looking at these videos and let other people smell these body odors. And then you measure the muscles in the face of the recipient. So if you have a person that's experienced fear or disgust, you can see that those typical muscles that you use to signal fear and disgust is more active.

17:51Mats Olsson:So fear sweat would smell different from exercise sweat.

17:56Katie Edwards:Well, these particular studies have shown is more this sort of low conscious type of communication. The studies where they actually, okay, smell this body odor and tell me, does this smell fear or happiness or disgust? They have not been so clear, I think. So if there is something going on, it might be bypassing some more elaborate conscious processing.

18:29Mats Olsson:I mean, obviously, then body odor must influence how we kind of judge or respond to other people. Why is smell then so strongly tied to attraction and make choice?

18:40Katie Edwards:One is sort of the idea of that it's hard to explain love and why you fall in love. So you say that maybe that you have chemistry as a metaphor and you know what's happening between other animals. So it's not a far-fetched idea that it would be part of an explanatory model why you fall in love, that you actually have a match. even though it makes a lot of sense it doesn't seem to really be clear that the nose is there to smell out and and again when it comes to that you really love the smell of the person you're in love with and my personal belief is that you love the smell because you're in love with that person

19:28Mats Olsson:and not the other way around right yeah so there's a t-shirt test isn't there where um researchers got a load of t-shirts that had been worn by men and then got blindfolded women to smell the t-shirts and say which ones they preferred. So do you think that humans have got pheromones or at least like pheromone type signals?

19:52Katie Edwards:I have earlier done some investigations looking at particular components of body odors that has been mentioned in the literature as putative pheromones. and yes if you look at hundreds of studies you will see that sometimes you see effects of body components but they are not especially easy to interpret and they are not so consistent between studies so if you would ask researchers in this field today i guess that no researcher or few researchers would say that we have this type of pheromonal communication that you can observe in other species it would be lovely we can find it my my guess my bet would be on the on the sort of area around the nipple i mean what could be more important to get the newborn child to find and be simulated to to suck on the nipple that's my guess if we'll find it we'll find it there first

20:55Mats Olsson:So do you think that a lot of what we think of as like good or bad smells then is more cultural than biological?

21:05Katie Edwards:Yes, very much, very much. If you look at sort of the newborn baby, it doesn't really have much of strong preferences for different odors. For us that have babies or had babies, you know how they can handle poop in certain ages. And then they learn that this is really not good, right? so I would say that more or less you're born with no preferences obviously odors can be stinging and painful but then you address another part of the system so then you learn this is good and this is bad and if it's nutritious you start to learn it and you can also see that in those vast differences in cultural preferences for different type of edibles I mean, here in Sweden, we have this sour herring that is almost word famous.

22:00Katie Edwards:And we're basically fermented, rotted herring. And when you open the can, it's like, oh, my God. If you're not sort of into that culture and you have sort of learned that this rotten smell is, you could work with it, right? because you'll sit, you'll have a party, you'll drink schnapps and eat other stuff and put sort of stuff on it that covers up a bit of the taste of it.

22:27Mats Olsson:I think I'd need quite a lot of schnapps for that rotten herring thing.

22:32Katie Edwards:Yeah, yeah, you need it for sure.

22:34Mats Olsson:It'd have to be a party for sure, yeah. There's a long history of linking illness with smell. So is there any, is there real science behind that?

22:43Katie Edwards:Yes, for sure. before we realized that this was about pathogens, germs, up to the middle of 1900s or so, there was an idea of how we got sick, that it was through bad air, like malaria. And also the word miasma means in Greek, something like bad air. So the idea was that what smells bad makes you sick. and that is a pretty good proxy because things that smell bad often contain a lot of pathogens therefore we think that we evolve the emotion of disgust to stay healthy and don't approach things that are bad for us and there is a lot of different types of reports a little bit anecdotal in the literature for instance scurvy that was found to smell putrid.

23:44Katie Edwards:And we also know like diabetes and make people get a certain acetone-like breath, a little bit rotten apple. And so there is a lot of anecdotal experience from that. And if you talk to caregivers or medical personnel that they will be able to smell out different types of diseases. Looking at more modern research, for instance, you have this field with dogs smelling out diseases. I mean, dogs really have a very good sense of smell. And they have now been shown to be able to smell a lot of things, specifically different cancers.

24:25Mats Olsson:You've run experiments, haven't you? Yes, I looked a bit on this.

24:29Katie Edwards:So we ran a number of studies where we had made people experimentally sick. How do you do that? We inject in the bloodstream something that's called lipopolysaccharides, which is essentially molecules from E. coli bacteria. But it's just the molecules. Yes, we do. So the immune system, they recognize that, oh, here's a stranger. Let's launch a systemic inflammation. So you feel as if you're coming down with the flu. You can get like one degree of fever and you get that typical sickness feeling. but then it just washes out because there's no pathogens there. And during this few hours, people are sort of technically sick.

25:16Katie Edwards:So we have been studying sort of the different sickness cues that appear in these individuals compared to when they come in another time, the same person, but just getting a saline shot. And then they're healthy, right? Then we can see that they express a number of tiny cues, like the skin color of the lips and the rest of the face changes a bit, and the emotional expressions, how they move. But we also realized from a couple of studies that within these few hours, they actually start to smell a tiny bit different. And on the scale from good to bad, a little bit towards they smell worse. so that it indicates that maybe this sensor smear can actually pick up like an early systemic signal of sickness.

26:12Katie Edwards:So these people do not sort of cough or sneeze, blow their noses or have any sort of rashes. They look kind of normal, just a little bit more tired and a little bit tiny differences.

26:27Mats Olsson:Matt, you've blown my mind a bit. So you injected him to make him a bit ill, and they smelled a bit different. How did you know they smelled a bit different?

26:37Katie Edwards:We collected their body odor by asking them to wear just cotton pads in the armpits. Yeah. And then we put these armpit pads in jars, and then we just let other people smell them. in a study

27:00Mats Olsson:oh my god this is the best study ever

27:03Katie Edwards:well it's not that bad because I mean people are instructed to use scentless soaps before they come in so these odors are very very in most cases very faint so you could hardly feel something there

27:18Mats Olsson:so how did you describe it then

27:21Katie Edwards:well we actually try to see whether they will sort of some odor quality will will pop out you know that they now people smell more like cumin or something or yeah but it didn't turn out so they simply the only label they used more commonly for people that were sick compared to healthy was that they smell more sweat so that typical sweaty odor that is we typically are not very fond of they smell more of that and that's why they smelled worse oh interesting because i was thinking that it would be more of a sour smell uh yes but i don't think it came out quite significant do you have any experience of your sort of family members yeah because that's what

28:12Mats Olsson:i was sour when they're sick that's what that's what i was thinking but maybe it's just that i mean you might have just come across a rare talent here matt that i can i can you know sniff out

28:24Katie Edwards:illness actually what you're talking about there that maybe you can and the thing is that we have a few hundred odor receptors in our olfactory epithelium up in the nose. But they vary a bit. So I may have a few that you don't have, and you may have a few that I don't have. So that makes that people are quite different in what they can smell. Some people think that coriander doesn't fly at all. Like you, you probably have that receptor. So it becomes too strong and maybe reminds you about the soap or something, maybe? I just, I cannot eat it.

29:03Mats Olsson:It sets my salivary glands off like I want to be sick. Yeah, yeah. Okay, yeah. Honestly, I think you've found a talent. I'm just...

29:11Katie Edwards:Yeah, what I'm saying that it could be actually that you have receptors that are not so common and make you good at smelling out certain types of disease. I mean, actually, there is a famous example of a woman that started to smell out Parkinson's. The story was that she noticed that her husband's shirt started to smell different from the neck here. And then he got Parkinson's. And then some researcher thought this was interesting. And she was tested with a number of Parkinson's body odor shirts and some healthy ones. And this story has it that she sort of really nailed this test, more or less.

29:56Katie Edwards:And then following that in the UK, there has been quite a number of studies looking at Parkinson's. And they have seen that if you analyze the sebum, I mean, that oily thing on the skin that protects you, it seems that it has another composition than healthy people.

30:15Mats Olsson:Could body odor ever become a reliable diagnostic tool in medicine?

30:20Katie Edwards:Yes, I think so, because there's also a whole new field now inspired by this idea of that disease smells. And that's called e-nosis. For instance, take Parkinson as a theoretical example. OK, Parkinson smells. Now, researchers are trying to decipher which molecules differ between healthy and sick. And if you know which molecules differ, you could build an enose that directly targets those molecules. And then you would have a very easy and non-invasive device for diagnosing diseases. So it makes sense. It's just you need to do a lot of science to get there, because if you take body odor, it's not about a few components.

31:14Katie Edwards:We talk about hundreds of molecules. And in that bouquet of many molecules, find what is different is very hard. Wow. Well, that's absolutely fascinating.

31:26Mats Olsson:Thank you so much for joining us today, Matt. Well, thank you. Professor Mats Olsen, who is a professor of experimental psychology in the departments of clinical neuroscience at the Karolinska Institutet in Stockholm, Sweden. I'm Gemma Ware, host of the Conversation Weekly podcast. Each week, I speak to an academic expert about a topic in the news to understand how we got here from global politics.

31:52Dan Baumgardt:World War II has this very long shadow in all of East Asia because there's a lot of unfinished business.

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32:42Mats Olsson:I just found that absolutely fascinating talking to Matt because, you know, I started off just thinking about, you know, body odour and the way that, you know, we're kind of taught to think about it. But then talking to Matt made me really reframe it because it's exactly like he says, it's more social than it is biological. We get sold all this stuff to try, especially women get sold all this stuff to try and kind of contain and cleanse. And the idea that natural bodies, there is something deficient or there's something wrong with them, or there's something that we have to be worried about. We've got to be constantly concerned that we smell in some way, that, you know, our breath's bad or, you know, we've got BO.

33:26Mats Olsson:But actually, you know, humans just naturally produce scent and that carries information, important information. So, yeah, what did you think about Em? Yeah, absolutely. I completely agree.

33:37Dan Baumgardt:It's a normal part of life. It's a factor of sweat and it's a factor of bacteria. And the bacteria we have on our skin is just really a part of life. It's our microbiome. It's normally there. We can scrub and scrub to try and get rid of it, but it will always bounce back.

33:52Mats Olsson:But for people who are genuinely concerned about body odour, what can be done if you want to reduce it?

34:01Dan Baumgardt:You've got to think about the ways in which you can practically reduce body odour. And it is repeated short term solutions looking at reducing the bacterial count on your skin and by reducing sweat. Simple measures like washing can help clear the sweat and wash away the bacteria that might be starting to get a little bit frisky as a result of that, all that sweat production. but you'll also see that some people are making use of things like antibacterial treatments soaps and alcohol and benzoyl peroxide which is another agent which some people use for acne

34:33Mats Olsson:i don't know if you've ever seen it before yeah i've seen people on social media using

34:37Dan Baumgardt:benzoyl peroxide and also glycolic acid yeah yeah it's sort of natural things like tea tree oil and stuff which people use but benzoyl peroxide can have some really good effects but you've got to be aware of the side effects it can bleach all your clothes and your bedding and it can also bleach your skin you've got to be aware of the effect that all of these things are having on your skin so things like um antibacterial soaps with harsh chemical agents in it or alcohol can dry the skin out and and affect its function um they can irritate it they can even alter those bacterial colonies on the skin for the worse as well now for people who get really sweaty as well i don't know if you've also seen some people are resorting to botox infections yeah why would you do that?

35:18Dan Baumgardt:So some people do naturally sweat more than other people. And some people have a condition called hyperhidrosis, which is just basically the medical term for increased sweating. So sweat glands activate more and release more sweat onto the skin. And that can sometimes cause embarrassing sort of sweat patches in different areas, which makes some people very, very self-conscious. So Botox can help switch off that sweat response and it can prove really, really effective in some people.

35:44Mats Olsson:But with antiperspirants and stuff, I mean, obviously there's a difference between antiperspirants and deodorants. Yes, there is. What is the difference? What are they doing, the different types?

35:54Dan Baumgardt:Well, antiperspirants basically contain aluminium salt. And when you spray that under your arms or in any other area of body, what it effectively does is it forms a little series of microscopic plugs, which effectively go into the sweat glands and prevents the sweat from coming out. And is that okay? Yeah, it's fine, but it's not something that stays there permanently. It's a plug that just stays on for anything from a couple of minutes to even a couple of hours. What's the difference with the deodorant then? These different deodorants and different agents are, some of them are fragrance-based, some are true antiperspirants.

36:28Dan Baumgardt:A lot of them, body sprays, may just have fragrances in them, which are just designed to mask the smell. In fact, that's what they used to do back in sort to medieval times there was a lot of masking of smell going on they had perfumed hankies and perfume gloves and other things in order to mask smells and it's a tradition that's carried on

36:45Mats Olsson:i think i'd rather smell like somebody's body odor yeah than smell that really strong perfume you know when you're on a train or something and you're gagging on like whatever perfume they've got and it makes me feel sick like it actually gives me travel signals or if someone in the

37:02Dan Baumgardt:office is dousing themselves in in aftershave and you're sat in this pack of raban hothouse getting you know sort of like other aftershaves are available i think it's pack of raban personally that i do i have a bit of an aversion to um but um yeah it's it's it's an age-old formula and again sort of back in medieval times apothecaries and old physicians believed it was an imbalance of those body humors and so they would resort to sort of things like that old chestnut bloodletting or perhaps giving you a pint of vinegar to quaff. Personally, I'd rather stink, if I'm absolutely honest with you, rather than having to resort to those.

37:38Mats Olsson:Yeah, having a few leeches put on just because you're, yeah.

37:42Dan Baumgardt:But yeah, these different deodorants and different agents are, some of them are fragrance-based, some are true antiperspirants. And you can also get some stronger antiperspirants as well, particularly for people who sweat more and are conscious of that, with higher levels of aluminium salts in them. But they're usually reserved for people who've got really severe or more persistent sweating problems. And when's best time to put these things on? Well, the trick is actually best to put them on when the skin's dry rather than wet. And that's simply because you've the problem that if your skin's wet, the deodorant or sorry, the antiperspirant, I should say, is much less likely to create a plug on the skin.

38:19Dan Baumgardt:So don't do it straight out the shower or make sure you dry off properly, first of all. And the other thing is what is often quite better at nighttime because your sweat glands are less active because you're less active overnight, it means that those little plugs are more likely to form.

38:34Mats Olsson:Oh, Dan, you do know some stuff, don't you? A couple of little tricks of the trade. So what have we learned then in this episode, Dan? Well, what I've learned personally is that science doesn't support the level of concern that there is around body odours. Most body odours are normal. It's healthy. It's driven by bacteria, just doing what bacteria does. chlorophyll might have some applications in very specific settings but it's unlikely to do anything miraculous and you know so i think i think that you know body odor has just become something else to try and sell us as a problem rather than just being a natural thing and a natural thing that we

39:15Dan Baumgardt:shouldn't be worrying about as much i think that's right our discomfort with body odor says about as much as uh social expectations and insecurity as it does about the biology i agree damn huge

39:27Mats Olsson:thanks to Matt Olson at Karolinska Institutet in Sweden for helping us unpack all of this.

39:33Dan Baumgardt:And if you enjoyed this episode, hit subscribe, leave us a review and share it with anyone who's ever wondered whether their deodorant's actually doing anything at all.

39:41Mats Olsson:And if you've seen a claim online and thought, get away with it, that can't possibly work, then we want to hear from you. email us at strangehealth at theconversation.com that's strangehealth all one word at the

39:58Dan Baumgardt:conversation all one word dot com strange health is produced by Gemma Ware with editing and mixing by Anouk Millet and artwork by Alice Mason thanks very much see you next time bye everyone bye

40:13Mats Olsson:Jane Austen's characters jump to life on screen with a new adaptation for each generation but 250 years after her birth, Austen herself remains an enigma. When she died aged as 41, Jane's sister Cassandra burned most of her letters. What's left gives us tantalising clues about who she really was. I'm Anna Walker, host of Jane Austen's Paper Trail, a new podcast from The Conversation. Over six episodes, one for each of her books, will take you on a journey through Austen's life and times with the help of the UK's top experts. From a scandal-filled tea room in Bath... She obviously had quite a sharp pen for the cutting remark.

40:54Mats Olsson:...to a windswept walk along the seashore at Lyme Regis. Austen herself envied the wives of sailors and soldiers because of the freedom, the liberty that you feel at the seaside. Listen to Jane Austen's Paper Trail wherever you get your podcasts.