Science Vs - Deodorant: Is It Dangerous?

Episode Date: November 10, 2022

Today, we’re diving into your armpits! We’ll find out why some of us are so freaking smelly. And then we’re asking: Are deodorants and antiperspirants safe, or should we ditch our sticks? We’ll talk to microbiologist Professor Gavin H Thomas, microbiologist Research Associate Professor Julie Horvath, epidemiologist Associate Professor Hanno Ulmer, and epidemiologist Professor Julia Knight.  Here’s a link to our transcript: https://bit.ly/sciencevsdeodorant  This episode was produced by Meryl Horn, with help from Michelle Dang, Disha Bhagat, Rose Rimler, Courtney Gilbert, and Wendy Zukerman. We’re edited by Blythe Terrell. Additional editing help from Caitlin Kenney and Nicole Beemsterboer. Wendy Zukerman is our Executive Producer. Fact checking by Erica Akiko Howard. Mix and sound design by Bumi Hidaka. Music written by Bumi Hidaka, Emma Munger, Bobby Lord, and Peter Leonard. Thanks to all our listeners who left voicemails about their stinky pitties. And a big thanks to the researchers we spoke to, including Professor Philippa Darbre, Dr. Andreas Natsch, Dr. Rianne de Ligt, Dr. Cory Hartman, Dr. Kanika Khanna, Dr. Chris Callewaert, Dr. Caroline Allen, Professor Kris Graham McGrath, Dr. Adeline Kikam, Dr. Jamie Alan, and Professor Cornelia Baines. Special thanks to Krystal Hawes-Dressler, Hannah Chinn, Stevie Lane, as well as Jonathan Goldstein. He read our old timey deodorant ad. By the way, Jonathan’s show, Heavyweight, is BACK! The new season is here and it’s great. You can find it here: https://spoti.fi/3hB3F9a  Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hi, I'm Meryl Horne filling in for Wendy Zuckerman, and you're listening to Science Versus from Gimlet. This is the show that pits facts against foul odors as we tackle deodorant. Because it turns out that a lot of you are really stinky. Hi, I'm smelly. I have the worst body odor. I've always been a pretty stinky person. I don't know why the heck I am so smelly.

I mean, this happens to people that we all know and love. My sweat smells so bad that my mom used to, like, smell me before I even reached the house and be like, Wendy, take a shower. Yep, even Wendy's a stinker. So it seems like the obvious solution here is to slather on some deodorant or antiperspirant. But a lot of you were like, hold on a second. What exactly is in this stuff?

Like, some of these sticks and sprays are chock full of chemicals. So, are they really safe? I know that I've heard a lot of buzz about different metals in deodorants and the risk of breast cancers. And I would really like to go back to using an antiperspirant. But I'm terrified of, like, what is in it. I'm just worried now about chemicals in the deodorants and how it's affecting me. Because of this, some of you have made the switch to so-called natural deodorants. And you're not impressed. Either the natural ones smell really bad or they don't work.

I started trying out a bunch of natural options and my bedside drawer became a graveyard of failed attempts. So let's dig into our bedside drawer of science. Today, we're going to look at why some of us get so smelly and find out what are deodorants and antiperspirants really doing? And are they dangerous? Come along as we dive into your armpits. Because when it comes to deodorant, there's a lot of... Wendy, take a shower. But then there's science. Science Versus is coming up after the break. Bumble knows it's hard to start conversations. Hey.

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It's season three of The Joy of Why, and I still have a lot of questions. Like, what is this thing we call time? Why does altruism exist? And where is Jan Eleven? I'm here, astrophysicist and co-host, ready for anything. That's right. I'm bringing in the A-team. So brace yourselves.

Get ready to learn. I'm Jan Eleven. I'm Steve Strogatz. And this is... Quantum Magazine's podcast, The Joy of Why. New episodes drop every other Thursday, starting February 1st. Welcome back. Today, we're taking on body odor and the stuff we use to fight it. And to start, we wanted to know, where does BO come from? Why do we smell? So we called up a scientist named Gavin Thomas. And when we got to chatting, he told us about a presentation he had to give when he first got into this BO world.

And I remember going down and being a bit nervous and walking into the room to do my presentation. Actually thinking, oh my God, I can smell some BO on me. And I was like, this is a come to do a project about trying to stop oleodiproduction. So in addition to being a bit smelly himself, Gavin is a professor of microbiology at the University of York in the UK. And he told me that the reason we have BO,

it all comes down to the microbes that make their home on our bodies. So, to understand how this happens, imagine that you were a bacterium on the human body. Where would you live? Well, you could pick something like the forearm or the elbow, but those areas are pretty dry and exposed. It's pretty hard to live there, sort of like camping in the desert. A much better place to live would be the secluded, moist oasis of the armpit. And you're not the only one who wants to live there. So you've got a really, really an area which is stuffed full of microbes all happily chomping away on sweat secretions. So it's a great place to be.

One reason this is a great place to be is that there's a buffet full of tasty bacteria treats. It's your sweat. Your armpit makes two main kinds of sweat. One kind is that salty liquid that trickles out when you're going for a jog. And this is the stuff that cools your body down. But the other kind, the kind that the bacteria love to eat, is this special sweat. It is much more complicated. It would look like kind of a thick, milky kind of liquid if you looked at it. If that other sweat is basically salt water, this special sweat is kind of like a milkshake. So yeah, my milkshake brings all the bacteria to the yard. All right. Anyway, for bacteria, this is the good stuff. And scientists don't really understand why we make this special sweat.

Whether or not it serves any real purpose is a mystery. We start pumping it from our pits in our groin and a couple other places around puberty. And bacteria love it because it's full of fats and other stuff that they can chow down on. So they can get food out of it. And then the molecule that's left, they spit out. And those molecules they spit out, those are the real stars of today's episode. That's what BO is. I asked Gavin, is BO sort of like the bacteria poop? Yeah, kind of. Yeah.

Your sweat itself is odorless, but that sweat gets eaten up by the bacteria who poop out these chemicals, and that is BO. And there are dozens of these smelly BO chemicals, all made by bacteria chowing down on different stuff in that milkshake sweat. Gavin actually works on one of the stinkiest BO chemicals. He said it sort of smells like a cheesy, oniony, sulfur-like stench. It's really gross. One time, a grad student spilled a little on his lab by mistake. I like that tiny, tiny amount, and the whole department stank of body odor for a few hours.

So this is really, really, really, really pungent stuff. And that's just one of the chemicals that make up BO. Everyone has their own signature BO cocktail. Like some of these chemicals wafting off our pits have more of an acidic, spicy smell. There's even one that's known as a pig pheromone and one called goat acid, which smells like goats. Okay, so that's where BO comes from. Bacteria in your armpits eat up this special kind of sweat and then basically poop out chemicals that can waft through the air. And this explains why some of us are smellier than others. We may have more of those bacteria that make the really stinky chemicals. Others may have less of them. And this also has to do with your genetics. Like there are some people who just don't really have stinky pits.

Scientists have found that a lot of them have this particular genetic mutation that changes what's in their sweat, which means they basically don't give off that oniony chemical. And so for them? So their overall smell is quite different. Their odor is much less pungent and is described as being more sweet. This mucation is most common in some places in East Asia, like Korea and China, where it's actually the norm. Something like 80 to 95% of East Asian people don't have stinky pitties. But many of us aren't this lucky and do have stanky BO.

And for a long time, we've been told that we need to do something about it. That's where deodorant and antiperspirants come in. In the U.S., deodorant started hitting the market around 100 years ago. And to get people to start buying this stuff, companies had to convince them that it was necessary in the first place. So ad campaigns were born, telling people, especially women, that if they didn't start using deodorant, they'd basically die alone. Here's one newspaper ad from the 1930s. You're a pretty girl, Mary, and you're smart about most things.

But you're just a bit stupid about yourself. You love a good time, but you seldom have one. Evening after evening, you sit at home alone. You've met several grand men who seemed interested at first. They took you out once, and that was that. Wake up, Mary. Yeah, it turns out that the cause of Mary's loneliness was, you guessed it, BO. We found tons of ads like this, and the industry has exploded over the years. The vast majority of people in the U.S. wear deodorant, 90% of us. So our next question is, how does this stuff work? Like, what's really going on in your armpit when you slather this stuff on?

We're going to focus on antiperspirants, because those are the big guns that help stop you from sweating. And for this, we're going to talk to Julie Horvath. Hello! Hi, Julie. Julie's the head of a research lab at the North Carolina Museum of Natural Sciences. She's helped get at what's going on here by studying what deodorants and antiperspirants are doing to the bugs in our armpits. Her first study actually began after she and her lab mates were basically just swabbing their armpits for fun. You know, as scientists do. We wanted to sample things where we found smelly body parts, so we sampled armpits.

They put the stuff from the swabs onto petri dishes, and then after a couple days, checked to see how many bacteria had grown. And a couple people had some really interesting things growing on their plates. And I thought, oh, that looks really cool. I wonder what's on mine. And then I went to all of my plates, and they were all blank. Nothing was growing. Nothing at all. Julie thought back about why this could be and realized what might be happening. When she first started her job at the museum,

it was a little nerve-wracking. I was a little bit shy, and now I have this prominent role where I'm supposed to talk to the public every day. And so I had started using clinical strength antiperspirant deodorant. And so probably all those chemicals I was using on my skin had killed off the microbes on all these places that we had sampled. And so that's why there was nothing growing on my body. You were like going nuclear on them. Yeah, exactly. Yeah, I got rid of all of them. But Julie was just one person. To see if this happens for other people, she and her colleagues went on to do a small study on this to look at what happens to the microbes on our armpits when we use antiperspirants.

Julie's team started by getting people to let their bacteria run wild. So they got 18 people and told them to stop wearing anything on their armpits at all for several days, and then watched as their armpits became chock full of bacteria. Meanwhile, they were bringing all these people into the lab to get swabbed. You know, when we were doing the sampling, our lab definitely had a fragrance to it. The next step was to see what an antiperspirant would do here. So they gave them one to use for a couple days, and... And then everybody had a drastic reduction in the amount of microbes that were living on their skin. How big a drop was it? I

mean, really significant, you know, from hundreds of cultural microbes on these people's skin went to maybe just one or two or a handful of microbes living on their skin that we could culture. So a dramatic, a dramatic drop in what was on the skin. So antiperspirants basically stop the bacteria from pooping and stinking up our pits. And the way they do this is actually pretty wild. The antiperspirant products are things that have aluminum-based salt. So the aluminum-based salts will actually mix with your sweat when you do sweat, and then it actually makes essentially a plug so that it reduces the amount you sweat in the future. Yeah, this is the infamous aluminum. It's a key ingredient in a lot of antiperspirants.

When you use these little bits of aluminum mixed with the stuff on your skin to clog up your sweat glands, and that physically blocks sweat from coming out. And with no sweat, a lot of the bacteria will starve. So that's the secret weapon that antiperspirants have up their sleeve, aluminum. Companies will throw other stuff in these sticks too, like antimicrobials and fragrances. And just quickly, we heard from some of you who are worried about this idea of blocking your sweat glands, that this could somehow cause toxins to build up inside your body. But that's just a myth. It's mainly your kidneys and liver that do the detox thing. And then most of that grotty stuff gets flushed out through your pee and poop. Bottom line, RBO comes from the bacteria eating up this special sweat and pooping out

smelly chemicals from it. And antiperspirants work because aluminum clogs our pores and blocks that sweat from ever even coming out, which shuts down that bacteria buffet. But is this safe, rubbing metal all over our pits? That's our next pit stop after the break. Welcome back. Now we know what BO is and how antiperspirants block it. But next, we're going to look at whether we should be worried about what's in this stuff. And some of you had asked us about parabens, but a lot of these sticks and sprays don't actually use those anymore. So we're going to focus on the aluminum that we just talked about. Because there's this idea that it could be seeping into our bodies and doing damage. In particular, people have been worried that it could be causing breast into our bodies and doing damage. In particular, people have been worried that it could be causing breast cancer or maybe Alzheimer's. Over the years, claims have been made

that deodorants or antiperspirants might be linked specifically to breast cancer. There's a growing amount of research directly linking aluminum, specifically the aluminum that's found in deodorants, to causing breast cancer and other dysfunctions in the body. Yeah, what is this stuff doing to our bodies? Let's start with cancer. When I started looking into the science here, right away, I found that there is some evidence that aluminum isn't good for us. Like, if you put aluminum on cells in a dish, it can make them behave more like cancer cells. And one weird thing is that a study did find that more breast tumors have been popping up near the armpit, right near where we put on antiperspirant. And then in 2017, a study came out

that sounded even scarier. We called up one of the scientists who did it, Hanno Ulmer. Hello. Oh, hello. Hanno is an epidemiologist at the Medical University of Innsbruck in Austria. And he wanted to dig into this to find out whether deodorants really could be linked to breast cancer in people. So his team got around 400 women. Half of them had breast cancer, half of them didn't. And they asked the women how often they had worn this stuff under their arms when they were younger. So never, once in a month, several times a month, several times a week, daily or more than daily.

By the way, they couldn't separate out the people who wore deodorant with aluminum in it because a lot of women had no idea what was in their deodorant. So they just asked everyone about underarm products in general. And Hanno told me that none of the scientists doing the study thought that they'd see a link to cancer. So you weren't expecting to find anything? Actually not, yeah, yes.

The surprise was that there was an effect. There was a difference between the groups. You found something. Yeah. They found that the women who said that they had worn the stuff more, they were more likely to have had breast cancer. And in particular, the women who wore a lot of deodorant, those who put it on more than once a day, they were the ones who had the increased risk. And then Hanno's team wanted to see if people with cancer actually had more aluminum in their breasts. So they looked at breast tissue from some of the women with cancer and some of them without it. And here's what they

found. Aluminum content was higher in the breast cancer patient group. It was not a big difference between the groups, but there was a statistically significant difference. Yeah, the women who had breast cancer had a little more aluminum in their breasts. So when we first saw this study, it was looking pretty bad. Like wearing a lot of this stuff could increase your risk of breast cancer.

Maybe because it lets more aluminum seep into your breasts. But you might not need to throw away your antiperspirant just yet. And to explain why, here's Julia Knight. She's a senior investigator at the Lunenfeld Tenenbaum Research Institute at Sinai Health in Toronto. Julia said that while some of this research sounds scary, there are actually a bunch of caveats that you need to know. I always get worried when people, when things get in the

media, like this study shows X. Well, that's fine. Well, what about the other studies that have been done? You have to think of it as sort of like a court case. This one study is sort of like, it's sort of like a situation where there's been a murder and one witness reports seeing you near the scene of the crime. We don't convict somebody on that basis, right? You have to think about that, that it's just one little piece of evidence. Yeah, so to really be worried about what Hano found, you'd need other witnesses, other studies to back it up. And in this case, when we look at the other papers on this, they're all over the place. For example, another study like Hano's didn't find a link at all between deodorant use and breast cancer.

Another problem is that the witnesses in these studies may not be remembering things right. Because they're asking women to think back about their deodorant habits from decades ago. And Julia says that asking people with cancer about this kind of thing is especially tricky. If you have a serious disease like breast cancer, you're going to think a little differently about, because you're probably trying to think like, why did I get this? What might explain it? You know, you think a little bit. And so in this case, it could be that you're more likely to think like, oh, I think I've heard that deodorant might be linked to breast cancer. And like, maybe I did use a lot when I was younger. Yeah, for sure. That sort of

thing. I mean, that's a very common problem we call bias. Julia says that because of these issues, she's not convinced that there is a link between antiperspirants and cancer at all right now. A lot of other scientists that we spoke to agreed with Julia. We asked Hanno about this. He's the one who worked on that scary-sounding study on the 400 women. Do you think that your study is enough to convince you that this is dangerous?

No, we can't say. It would be absolutely too much to say that our study is a proof for the relationship between aluminum and breast cancer. Okay, so before we leave this question on whether antiperspirants are bad for us, we wanted to look at the idea that antiperspirants might be linked to Alzheimer's disease. And what we found is sort of similar to breast cancer. The research is kind of all over the place. So we reached out to a bunch of experts.

We heard back from six of them, and they all said that at this point, they're not worried about the aluminum and antiperspirant leading to Alzheimer's. So bottom line, we don't have good data showing that antiperspirants can up your risk of getting breast cancer or Alzheimer's. So bottom line, we don't have good data showing that antiperspirants can up your risk of getting breast cancer or Alzheimer's. Where does that leave us? Well, if you want to keep using antiperspirants, you're probably fine. But there is one thing that some scientists mentioned. Maybe don't use antiperspirant if you've got a cut on your pit, like if you get a nick while shaving. The FDA says that antiperspirants are generally considered safe, but you shouldn't use them on broken skin, so you can limit how much gets into your body. The FDA also says to

watch out if you have kidney disease, to check with your doctor first. Okay, so let's say you do want to abandon your antiperspirant altogether. What are your options? Does anything else actually work? Well, if you look at TikTok, you'll hear people talking about all sorts of stuff. You can use apple cider vinegar as deodorant. This is glycolic acid, and it eliminates the underarm bacteria that causes BO. I have the best deodorant hack ever. Any kind of salicylic acid toner. Other people are just using lemons. One person who got on the lemon train is rapper Sweetie.

She mentioned this in an interview that she did. Put lemons instead of deodorant on your armpits. So just to, like, prepare it, you might just want to squeeze it to get the juices flowing. And this did kind of get our juices flowing because it makes sense. A lot of these things are acidic, which could kill off some bacteria. So I looked for studies on these things. At first, I came up short, but then I asked Julie Horvath, our pit swabbing scientist from earlier, and she actually has done a tiny bit of research on this. We actually did a lime study where we had people who applied lime juice to their armpits.

Like they were just rubbing lime slices on their armpits? Yes, uh-huh. And then we saw it grew on the plates. And the plates showed that the limes were working a little, but they only tried it on two people, and there was a problem. People just said that they didn't really like the effect of the lime juice because, you know, maybe it was killing off some of the microbes because changing the acidity, but it made them really sticky. And so they weren't a fan. But again, this was only two people, and we

couldn't find much evidence on any of these other trends either. All right, so what about so-called natural deodorants that you can buy in the store? Like the ones that have the stuff to kill off the bacteria or mask the smell, but no aluminum-based antiperspirant. We wanted to know if those actually kill off the stinky bacteria, but the data we have on those is also pretty underwhelming. Julie told me about one small study of nine people. It found that the natural deodorants did work to kill off some bacteria, but it didn't work as reliably as the antiperspirants. The deodorants do work for some people, and it probably works better in some people than others. And the some people versus others,

it's not really clear who it works in and why yet. But, I mean, it works at some level. But Julie says that there is one thing being tested in the lab that she's excited about, probiotic deodorants. Like, maybe the answer is that we should be working with our armpit microbes, not against them. You could do this by adding more of the good guys to the mix, the less stinky bacteria. This is what probiotic deodorants try to do. They actually have live organisms in them. And some of these live organisms you can put on your body and they will eventually, you know, over multiple days or weeks,

replace the microbes that live on your skin that are smelly. So you can use that as a deodorant. There's one small study on 10 smelly people which did find that this worked to make them a little less stinky. And at least one clinical trial is in the works. So who knows? But Julie's optimistic that swapping your stinky microbes for some more neutral ones might help. Or maybe find somebody who smells really good and get a transplant from them

and see if those microbes can out-compete your smelly ones. Like rub armpits against them? Yeah. Yeah, that would be a little tricky. I haven't heard of the rub armpit parties. That's an interesting party. And there are other options that might be worth trying for people who are dealing with really bad BO or sweating. For example, Botox seems to work pretty well for the super sweaters.

According to one review, it made them sweat 80 to 90% less. It's temporary, though though and can be expensive. But if you're ready for the most radical solution we heard when it comes to BO, here it is. Embrace your stink. We heard from a lot of you who are like, F it. I haven't used deodorant in probably 10 years or more. I just go with the natural B.O., make life miserable for everyone else. Just kidding.

But my kids do make fun of me quite a bit when they can smell me and cross their own. My preference is not to use anything. I don't use anything. I don't believe we need it. Sometimes, yeah. Sometimes I smell. And I like to smell like a human being instead of

like a flower or a rose petal. That's Science Versus. Hi, Meryl. Hey, Rose. Meryl, how many citations are in this week's episode? There are 65 citations in this week's episode. And wait, actually in my version it says 63. Did it change? I know, but I'm going to add a couple more. Oh, okay, okay, okay. So I'm going to, yeah, you got me. And where can people go to check out these citations? They can go to our show notes and then follow the links to our transcripts.

Rose, did you change anything about your deodorant use after working on this episode with me? No, but I already was using an aluminum-free deodorant. But I didn't have any strong feelings about it. I just sort of, I don't know. I can't really explain why, but I guess I'll keep doing that. Yeah. How about you? Before, I didn't really wear any deodorant, and this episode sort of reminded me that it exists. And so now I do put it on, but it's kind of randomly. What? So now you wear more deodorant than you used to? Yeah. All right. Well, nice job, Meryl.

Thanks. Bye, Rose. Bye. This episode was produced by me, Meryl. Thanks. Bye, Rose. Bye. This episode was produced by me, Meryl Horn, with help from Michelle Dang, Disha Bhagat, Rose Rimler, Courtney Gilbert, and Wendy Zuckerman.

We're edited by Blythe Terrell. Additional editing help from Caitlin Kenney and Nicole Beamster-Bohr. Wendy Zuckerman is our executive producer. Fact-checking by Erica Akiko Howard. Mix and sound design by Bumi Hidaka. Music written by Bumi Hidaka, Emma Munger, Bobby Lord, and Peter Leonard. Thanks to all our listeners who left voicemails about their stinky pitties. And a big thanks to all the researchers we spoke to, including Professor Philippa Darb, Dr. Andreas Nash, Special thanks to

As well as He read our old-timey deodorant ad. By the way, Jonathan's show Heavyweight is back, and the new season is really good. If you're not already listening, definitely check it out. Heavyweight on Spotify. Science Versus will be back next week. Smell you later.