September 5, 2012 • 28 mins
Scientists are exploring why and how people's scents are as unique as fingerprints, and research finds that people can sniff out someone's personality, sexual orientation and age. Tune in to learn more about gender differences in body odor.
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Speaker 1 (00:00):
Brought to you by the reinvented two thousand twelve camera.
It's ready. Are you welcome to stuff mom never told you?
From how Stuff Works dot Com. Hello, and welcome to
the podcast. I'm Kristin and I'm Caroline, and we're talking
(00:21):
about something we've talked about before on the podcast, which
is body odor. Yeah, we didn't like us a long
long time ago, touching on gender differences in how our
bodies smell. And we've talked before about how scent can
(00:41):
be linked to physical and sexual attraction, and we are
going to touch on those things again. But there's some
new research that's come out and we had body odor
on the brain to begin with because of this minor
Internet sensation that happened a couple weeks ago with the
news that you could send people things called deodoro grams. Deodograms,
(01:07):
it's a nice way to tell somebody that they smell. Yeah,
it's a It's this natural care company called GB Proud
Foot that announced that they you could personalize a message
to someone in your life who stinks, and they would
send them this diodogram with a friendly message and a
(01:28):
yeah it came with a stick of something. Yeah, you
had a couple of smells to choose from, and also
different messages such as, for pitts sake, throughout your current
deodor and give this one a try. You deserve a
natural deodorant that works, you know, and message A which
is you've always been such a cute little stinker dot
dot dot. Well okay, yeah, whatever helps. I mean, you
(01:54):
don't want to embarrass your friend or person in your life.
I guess, Well, it's a touchy stuff jected to say, hey, hey, person,
you got some stinking going on. Yeah, well, you know,
sometimes people can't help it. They can't help what they
smell like. And maybe it's your problem, maybe you're too sensitive. Well.
And also what we're going to talk about more in
(02:14):
the podcast is the science that has developed around our
personal sense, like you and I each have and everyone listening.
It's like our our odors are actually more like fingerprints. Yeah,
and it depends on how old you are, what your
diet is, like, how much you exercise, how much water
(02:34):
you drank, all that stuff, where you are on your
menstrual cycle. It's true. Yeah, So before we get into that,
let's let's have a quick primer of where these scents
come from. Specifically two types of sweat glands that are
found on our bodies. The ekron which are the most
plentiful they are these are all over our body. They're
(02:56):
three million of them, roughly covering our skin. And the
apocrine sweat glands, which are not as plentiful, they're only
about two thousand of them. Yeah, So as your body
temperature rises, your autonomic nervous system stimulates the ekrone glands
to secrete fluid onto the surface of the skin. This
is mostly water and salt. It's too to kind of
(03:18):
cool you down. It's your air conditioning system. Now. Your
apricrine glands, on the other hand, secrete a fatty sweat
and directly into the tubule of the gland, and during
emotional stress or physical stress like you're you're running or
you're running around or you're stressed out, the tubule walls
contract and the sweat is pushed to the surface of
the skin where bacteria. You break it down. The bacteria
(03:40):
are all hanging out and they're like, man, when's our
snat getting here? I can can really go for a
sandwich or something. And then the sweat comes and they're like, yeah,
eating time, fatty sweat sandwich. Yeah, it's not it's not
the actual sweat that makes us smell. It's the fact
that our bodies are just covered with back area. This
(04:01):
is from the National Human Genome Research Institute. The ratio
of bacterial microbes versus skin cells on our bodies ten
to one. We're teaming teeming with bacteria. So really, if
you want to lose weight, you should just use antibacterial. So, yeah,
just get get rid of all of those, all those bacteria,
although you know, I mean, I'm sure they served the purpose,
(04:23):
but these all these microbes love to feast upon the
fatty sweat excreted by the apicron gland because they contain
something called a glycoprotein, which is a protein covered in sugar. Donut. Yeah,
so bacteria like nom nom nominal when we sweat sweat
(04:44):
donuts and sandwiches. That's that's really awesome. Um. Now, there
there's regular albio, which you know, and if you've ever
been to the gym or run or been outside on
a hot day, you've you've probably smelled yourself at some point.
You're like penny chick shower. But that's that's not really
a problem. Everybody's got bio everybody has a smell from
(05:04):
time to time, especially if you're not doing your laundry
or whatever. When it actually gets bad, it's called brom
hydrosis though, and that's the chronic condition in which excessive
odor emanates from the skin. And there's a bunch of
different health conditions that can cause you to smell anything
from just like excessive BO to actually having a fish smell.
It just kind of depends on health issues. Yeah. For instance,
(05:28):
um diabetes in particular is linked to BO. If you're
not monitoring your blood sugar and you have diabetes, you
can develop something called k o acidosis, which causes fruity
smelling breath and a pungent BO. Then also with thyroid problems,
if you have an overactive thyroid, the body might excrete
an excessive amount of sweat. It's interesting how how the
(05:52):
BO will will signal these internal issues going on. But
when it gets really bad, it's with this condition called trimethylaminuria,
which it's much easier to call it by its handy
acronym t M a U. It's when the body doesn't
break down this specific kind of amino acid properly, and
(06:13):
it causes a distressing fishy odor. Yeah. And the thing
is they tell you to avoid certain foods, but as
I was reading the list, I don't know what you
can eat because it says you have to avoid foods
like eggs, liver, seafood, beans, peanuts, broccoli, etcetera, etcetera. Like
there's a lot, there's a lot you cannot eat well.
And I'm sure for you, Caroline, eliminating the liver from yes,
(06:36):
I don't know liver sandwiches day in and day out
because you subsist off of cat food. Yeah, it's anything
that contains coline actually, And and again it's it reminds
me of our steliac disease episode where you have two
people with steliac haves to eliminate gluten, which is in
(06:57):
so much of of what we eat as well. Um,
And there was a two thousand eleven study speaking of
T M a U out of the monell Chemical Sensus
Center that found that a third of patients with an
unexplained odor who had that fishy odor that's you know,
that actually starts to affect like different areas of their life,
socialization and psychology because they have the smell, they don't
(07:18):
know what's going on. And they found that you know what,
the unexplained odor, it's the t m au. So if
you got a fishy smell going on out there could
be could be that the body doesn't processes amino acids. Yeah. Well,
there's also an effect that your diet has. We mentioned
diet meat meat. If you're a meat eater as I am,
(07:42):
apparently you don't smell as good as vegetarians. Yeah. This
was from a study called the Effect of Meat Consumption
on Body Odor Attractiveness that was published in the journal
Chemical Sense in two thousand six. Now, this was specifically
male meat eaters, and they had thirty women who were
not on any kind of hormonal contraception, which is important because,
(08:05):
as we've talked about before, birth control might tinker with
women's sense of smell. But they found that at least
among these thirty women, these smells of men who were
not or on a non meat diet were more pleasant, yeah,
less intense, significantly more attractive. So if you're looking for
(08:28):
a reason to go vegetarian, I guess these thirty women
would really appreciate it. Um. There's also if you want
to avoid just your run of the milby. Oh, you know,
they talk about strong smelling food like curry, spices, and
spicy food, because those actually do. Spicy foods increase your
body temperature. I mean, if you've ever eaten something super spicy,
you know you start to sweat. I'm a wolf and
I can't eat spicy food, so that's not a problem
(08:50):
for me. The problem for me happens to be garlic.
Not that I eat it all the time. I'm you
know whatever. I'm not trying to ward off any vampires
or anything, but onions and garlic are a volatile sulfur,
a substance, so look out for that. You can you
can smell back. Yes, we will excrete those smells through
all of those those pores on our body. Um. But
(09:13):
the thing is, you know, we we all have this
distinct bio whether or not it's amplified by something, you know,
condition like T M A U. Or for me, my
love of garlic and onions, I do cook with them
excessively lips uh. But you know, the thing is we
do so much to mask our own body odor. For instance,
(09:35):
there's a study which found that sevent of women and
sixty pc of men use a deodorant every day, while
forty percent of women also use it perfume every day.
We're just coding ourselves in sense. I wonder if that's
like a really American thing though, Like I feel like
that's very American to try to wash everything off of
(09:57):
you and not smell like your natural self. Because my friend,
her husband is from England and he doesn't use any
theater and he doesn't smell. Yes, there are differences among
like the body oder preferences by culture. So and I
have a feeling this was published in the Review of
General Psychology and it probably was from a Western study sample.
But let's get more into these unique smells that we have,
(10:21):
because you know what I'm all about, embracing our own
I mean, keep it, keep it under control, but embrace
your your your scent, your unique scent. Sure well, you
could call it your your fingerprint smell, or your odor
print or your scent print, if you will. The Journal
of the Royal Society interface in April two thousand seven,
(10:42):
researchers tested armpit, sweat, urine, and saliva from about two
hundred adults and found that the most volatile compounds were
actually in sweat, meaning that that had the strongest smell,
and they found and they were looking at it. They
found individually distinct fingerprints and a re producible difference between
the sexes. Yeah, they're referred to as genetically determined odor types. Um.
(11:08):
And there's another study which has found that you can
actually sniff out relatives in a way because of those
genetic links with your odor. Your relatives do kind of
all all smell similarly, which I can find fascinating. Yeah,
I don't go around. Maybe I should smell my mom more.
I don't know. Yeah, it's gonna make for some awkward
(11:29):
family or union moments, but you should do it. Thanksgiving,
you're going around just sticking your nose and people's necks
once they're taking their turkey naps. You just sneak up.
Yeah that Yeah, that makes for awkward hugs like, oh,
it's so good to see you uncle. Any Like, wait
a minute, you don't smell like me. Well, that whole like,
(11:49):
that whole constant that either genetic factor or that that
family factor that that seems to run. Um, it doesn't
change even if you change your diet. You know, we
talked about uh, spicy foods or garlic and onions. But
the Monell Center in October two thousand eight found that
an individual's underlying odor signature that that sounds nice is
(12:10):
still detectable even when they're major dietary changes. And they
also they use the term odor print. They say that
we have a consistent odor print, just like a fingerprint.
And it's not so surprising that we have the specific
odor prints because, as we've mentioned before, UM, scent is
one of the ways that we in humans instinctively UH
(12:33):
can determine someone's major histo compatibility complex in other words, UH,
their genetic difference to us, because if we a lot
of times, the people that smell the most attractive to
us have the most diverse major historic compatibility complexes, which
would mean that our offspring would have a better chance
(12:55):
of survival because you know, we want to avoid avoid inbreedings.
We're totally hurting the future of the human race, and
we put on deodora. That's what I'm hearing. Possibly it's true.
But let's get more into gender and sexual orientation, because
there have been a ton of studies UM around scent preferences,
and UH it's really interesting. For instance, UM, in one study,
(13:18):
straight women prefer the scent of dominant men, especially when fertile.
That's one. That's one of those studies where I wanted,
you know, like shake my fistic science a little bit fertile.
Do they use the word fertile fertile? Oh? Yeah, and
we uh. Straight women also tend to prefer the scent
of men with more symmetrical bodies. I can, I can
(13:42):
smell the shape of you. But at the same time, though,
there was another study out of the Archives of Sexual
Behavior from two thousand seven which found that I believe
this is also straight women again preferred the smell of
gay men's T shirts over straight men's T shirts. Yeah,
(14:04):
they had T shirts from gay men's, straight men and
just out of the package, like just off the rack,
and it was rated as like gay means were up
at the top, followed closely by out of the package
t shirts as far as like pleasant pleasantness goes, and
then straight men's T shirts came way behind. So you
hear that guy, straight duds out there, you kind of stinky. Well,
(14:28):
there was a there was an earlier study from the
Monell Center that they do a lot of smell research
over there. Good for you guys. Um, they had a
gay and straight men and women make preference judgments on
T shirts again. You know, you'd wear your T shirt
around and kind of get it all stinky and people
would judge it. Uh. They actually found a gay men
(14:48):
preferred odors from gayman and heterosexual women. So there you go.
Everybody has a preference, and it seems that women in
particular are maybe more a tune to this scent thing
than men might be. Uh. There was a survey published
in the journal Evolution and Human Behavior in two thousand
(15:09):
two which found that college women ranked body odor is
more important for attraction than looks or any other factor
except pleasantness. And what are the guys right as the
number one thing? Yeah, they looks as most desirable. Um,
and even in childhood there seems to be that gender difference. Uh.
(15:30):
This is from developmental psychology from two thousand three. They
had children and adolescents smell various odors and raithed them
for how much they liked it, and only the girls
disliked male sweat and could identify it. Yeah, And they
did a follow up experiment where they cued everybody into
the identity of the odors and then, regardless of gender,
(15:52):
adolescents over children disliked male sweat. More so they think
that maybe there's some sort of like social thing that
once you get older, you're like, oh men, men, sweat
that's dirty unless you're fertile and he's dominant apparently in
your a heterosexual fifty shades of uh oh. But speaking
(16:15):
of UM, I thought this was pretty fascinating. There was
an article published in May two thousand twelve in The
New Scientists by Mary McLoud all about scent and um
all of the most contemporary research about it, and she
cited a study out of Poland which found that participants
could by simply smelling people's sweat predict their personality type,
(16:40):
for instance, whether or not they were a little more
neurotic or extroverted. Um. Yeah, I mean the little more
pungent people were a little more erotic, but not erotic
neurotic or you know, maybe that was tested too, very
erotic sweat, um, But I thought it was It was
(17:01):
interesting that even even with personality, win for so much
from someone's scent, including their age. This is some of
the most recent research to come out, and this is
again coming from the Manel Chemical Senses Center, and they
were looking into this. The old stereotype about old people
(17:24):
smell for lack of better phrasing. Yeah, people tend to
find old people smell to be gross and off putting
and negative, and they don't have anything nice to say
about it. But that they think because the study that
might have more to do with the context, because they
didn't tell people necessarily that it was an elderly person
who had donated the smell. They just had all these
(17:47):
smells that they were testing, and the subjects managed, though,
to separate out the smells that belonged to the elderly.
They didn't, however, think they smelled bad or nasty or
off putting. They said that they smelled more pleasant than
the rest of them. Yeah. They had the participants divided
up into age groups and um by sex, and the
(18:09):
group that consistently smelled the worst. Guys, I'm really sorry
to keep keep on calling you out here, just stating
the facts. Middle aged men, you were the stinkiest lot.
But elderly men in particular, even more so than the
elderly women, had the most pleasant and almost non existent smell. Yeah. Well,
(18:34):
they point out that that might be because elderly men
have lost testosterone, so things are evening out in the
hormone area. But I thought, you know, like we have
we have this association I think with you know, it
goes along with nursing homes and retirement homes and those
very particular smells that are there, and once you remove
(18:56):
the older person from that context, and we kind of
this is so C eight the old people smell is
actually kind of figment of our imagining, at least in
a negative sense. Well, and the participants who donated donated
their scent. Uh, we're healthy, so there wasn't an issue
of any like health issues that might have been contributing
(19:16):
to a bad smell for instance. And this does that
that study from the Monnel Center does support a previous
study published in the Journal of Investigative Dermatology from two
thousand one, which found a specific component that's characteristic of
the body owner of the middle aged and senior citizens.
(19:36):
And they think it has to do something with changes
in our bodies in mono unsaturated fatty acid compositions of
our skin surface lipids. Yeah, quote unquote the deterioration of
the body owners for the middle aged and the elderly.
That's a nice way to put it. So like, so
are diminishing body grease? Yeah, basically, well, let's go to
(19:59):
somebody who's not greasy. That's babies. That's maybe the best
podcast transition ever been made. Well, Um, this this is
an interesting study. Uh, this is hormones and behaviors. New
moms are more attracted to the body odor of newborn
infants than are non mothers, even when they didn't know
(20:21):
the source. It's like they just like smell freshly baked
cookies and just go for it. It's like, I smell
something that needs nurturing in this room, a baby in
this room. Um. And they did find that mothers with
higher cortisol levels are better able to recognize their own
infants smells. Yeah, and it's a it's a two way
street too, because by two weeks, infants can distinguish between
(20:44):
their mother's breast milk and that of another mother and
they that's one of the quickest bonds to happen between
a mother and a child. Is that intense the baby
bonding to the mother smell and vice versa. Yeah, it's
really surprising how quickly infants developed that strong sense of smell.
I mean, they can't see very well and they certainly
can't tell you what's wrong. If they're crying, but they
(21:05):
can smell you, all right. Yeah, so yeah, familiar smells
they can soothe infants. You think about that, I mean,
if you think about it, like the the that intense
link between our old faction and memory and how that
you know, there's that tight um association in the brand.
I'm sure our sister or Brother podcasts Stuff to Blow
(21:27):
your Mind has done lots on the science of smell.
But just to finish things off with this smorgess board
of smells podcasts, let's talk about something called old factory
reference syndrome, which I had not heard of before you
(21:47):
sent me some info about it, Caroline. Yeah, I had
never heard of this, but you know, there's there's you
can be self conscious about the way you smell, Like
if you've been outside running around, you might be like, oh, gosh,
I hope I don't smell too bad, especially you know,
if you have to go back in to work or whatever.
But it's usually not debilitating. But there are people with
olfactory reference syndrome who feel that they smell so bad
(22:09):
that nobody would actually want to even spend any time
with them, be in the same room with them at all.
And these people usually fall into depression and shut out
the world. And this is from Catherine Phillips, who's a
psychiatrist at Red Island Hospital. They found that sixty of
these people have thoughts of suicide and thirty two percent
actually attempted. And they spend these people can spend somewhere
(22:31):
between three and eight hours a day obsessively thinking about
their various odors that nobody else can smell. So you're
sitting there constantly just in a state of high alert
like panic, thinking like, oh my god, you can smell
my feet. Can you smell my feet? You can totally
smell my feet. Well, a majority thought seventy thought that
the smell was from their breath, and then sixty percent
it was armpit smell, and thirty five percent thought the
(22:52):
odors were coming from their genitals and um. The doctors
think that at first they thought it was something to
do with ski staphrenia, but now they are seeing more
of as a link to O c D behavior. Yeah,
and so they usually try to treat it with cognitive
behavior therapy but also exposure therapy. So, no, you're going
(23:12):
to eat those onions and garlic and then you're gonna
go out and you're gonna socialize with people, darn it,
and so hope with the hope that that can actually
help them get over it. But even in the general population,
there is a link between heightened anxiety and a more
acute sense of smell, which is kind of fascinating and
(23:33):
and reminds me of our you know what animals we
are sometimes. Yeah. This was a University Wisconsin study in March.
They put a bunch of people in m r I
machines and and tested basically what happened in their brain
with the smell region of their brain and when they
were anxious. And they found that as anxiety arises, so
(23:55):
did the subject's ability to discriminate negative odors. And they
think that it is goes back to our evolutionary roots
of you know, threat detection and all of our since
that's going on high alert to keep ourselves safe. Oh
my god, the prairie tiger is going to kill me.
Somebody farted runway. Uh So I think that's all the
(24:18):
smell research that we have. Um My takeaway is, you know,
if a straightman smells very good, uh, maybe he might
be gay or very dominant, or a vegetarian or a
vegetarian all of these who doesn't eat spicy food or garlic? Indeed? Uh,
(24:41):
lots lots of fascinating takeaways. Oh, I've got one more
I forgot to mention. This was also from two thousand
and twelve in the Journal of Forensic Science. They found
that like police dogs trained dogs, Caroline, they are better
at sniffing out women than men. Well that's just not fair,
So lady criminals also be aware watch out. So that's
(25:07):
all we got, uh, Since b O any any BO
related stories we would like to hear from you listeners now,
Mom Stuff at Discovery dot com is where you can
send us your letters, and we got a couple here
to share with you. This one is from James. The
(25:30):
subject line is exciting fiction. Exciting isn't quote? So who
knows what he has in store for us? He says,
I'm a classicist and I thought i'd share some fun
facts about a it and the ancients when it comes
to exciting literature. The ours Amatoria comes in three books.
The first is for guys and teaches you how to
get a girlfriend. There's some really cute scenes, like how
to help your lady friend have a good time at
(25:51):
the horse races. That's my main concern, thank you. The
second is for ladies, teaching them how to get a boyfriend.
The third teaches you how to break up. We don't
know why Ovid was exiled. It's even possible that he
never was, and his poetry on the subject might be
some weird performance piece like what Joaquin Phoenix tried to
pull a few years ago. That's weird, and Netflix keeps
recommending that I watched that movie and I don't want
(26:12):
to um Appleus is Metamorphosis is a very funny, erotic novel.
It's mostly from the main character's perspective. He gets turned
into a donkey early on and stays that way almost
to the very end. The Greek novel is a genre
that's more like your modern day romance novel, with two
young lovers, pirates, kidnappings, fake death, et cetera. On the
(26:33):
visual side, he says, if you ever took a mythology
course or Roman sive, you probably saw some Pompeii and
frescoes of pre APUs, a Roman fertility deity with a
comically large fallace uh second bullet point. Greek base painting
from the classical period sometimes depicts graphic acts with the
characters fully disrobed. I'm not sure who would want their
olive oil shipped in that, but hey, different strokes and
(26:54):
all that. So thank you for the the saucy fiction
pointers Erotica. It's been around for agels. Well. I have
an email from Dima in Pakistan and this is in
response to our episode on donating old clothes, and she
has some pretty nep few ways that she deals with that.
(27:16):
She writes. My best friend's mom and I are usually
the people UH folks come to when they want to
donate something, especially clothes. So what we do first is
sift through them and separate them into two piles, horribly
ugly clothes slash unusable clothes and clothes people might actually want.
With the horrible clothes, I cut them and tie the
(27:36):
strips together until it forms something like a ball of
yarn for each item. With that yarn, my best friend's
mom will crochet a rug in about three hours while
she watches TV or something. She gives these rugs away
to anyone who wants them, and we plan on selling
some next year at our city's heritage festival. With the
usable clothes, we have created a swap with our friends,
(27:57):
which I'm making many people come to. So that's two
great ideas for clothing donations. And if you have any
great ideas or stories or just a hello to share
with us, you can send us an email mom Stuff
at Discovery dot com. You can find us on Facebook,
and you can follow us on Twitter at mom Stuff Podcast,
(28:20):
and you can check out our blog. We're on Tumbler now, folks,
that is stuff Mom Never told you dot tumbler dot com.
And as always, you can make yourself smarter by heading
to our website, It's how stuff Works dot com for
more on this and thousands of other topics. Is it
how stuff works dot com. Brought to you by the
(28:47):
reinvented two thousand twelve camera. It's ready, are you
Brought to you by the reinvented two thousand twelve camera.
It's ready. Are you welcome to stuff mom never told you?
From how Stuff Works dot Com. Hello, and welcome to
the podcast. I'm Kristin and I'm Caroline, and we're talking
(00:21):
about something we've talked about before on the podcast, which
is body odor. Yeah, we didn't like us a long
long time ago, touching on gender differences in how our
bodies smell. And we've talked before about how scent can
(00:41):
be linked to physical and sexual attraction, and we are
going to touch on those things again. But there's some
new research that's come out and we had body odor
on the brain to begin with because of this minor
Internet sensation that happened a couple weeks ago with the
news that you could send people things called deodoro grams. Deodograms,
(01:07):
it's a nice way to tell somebody that they smell. Yeah,
it's a It's this natural care company called GB Proud
Foot that announced that they you could personalize a message
to someone in your life who stinks, and they would
send them this diodogram with a friendly message and a
(01:28):
yeah it came with a stick of something. Yeah, you
had a couple of smells to choose from, and also
different messages such as, for pitts sake, throughout your current
deodor and give this one a try. You deserve a
natural deodorant that works, you know, and message A which
is you've always been such a cute little stinker dot
dot dot. Well okay, yeah, whatever helps. I mean, you
(01:54):
don't want to embarrass your friend or person in your life.
I guess, Well, it's a touchy stuff jected to say, hey, hey, person,
you got some stinking going on. Yeah, well, you know,
sometimes people can't help it. They can't help what they
smell like. And maybe it's your problem, maybe you're too sensitive. Well.
And also what we're going to talk about more in
(02:14):
the podcast is the science that has developed around our
personal sense, like you and I each have and everyone listening.
It's like our our odors are actually more like fingerprints. Yeah,
and it depends on how old you are, what your
diet is, like, how much you exercise, how much water
(02:34):
you drank, all that stuff, where you are on your
menstrual cycle. It's true. Yeah, So before we get into that,
let's let's have a quick primer of where these scents
come from. Specifically two types of sweat glands that are
found on our bodies. The ekron which are the most
plentiful they are these are all over our body. They're
(02:56):
three million of them, roughly covering our skin. And the
apocrine sweat glands, which are not as plentiful, they're only
about two thousand of them. Yeah, So as your body
temperature rises, your autonomic nervous system stimulates the ekrone glands
to secrete fluid onto the surface of the skin. This
is mostly water and salt. It's too to kind of
(03:18):
cool you down. It's your air conditioning system. Now. Your
apricrine glands, on the other hand, secrete a fatty sweat
and directly into the tubule of the gland, and during
emotional stress or physical stress like you're you're running or
you're running around or you're stressed out, the tubule walls
contract and the sweat is pushed to the surface of
the skin where bacteria. You break it down. The bacteria
(03:40):
are all hanging out and they're like, man, when's our
snat getting here? I can can really go for a
sandwich or something. And then the sweat comes and they're like, yeah,
eating time, fatty sweat sandwich. Yeah, it's not it's not
the actual sweat that makes us smell. It's the fact
that our bodies are just covered with back area. This
(04:01):
is from the National Human Genome Research Institute. The ratio
of bacterial microbes versus skin cells on our bodies ten
to one. We're teaming teeming with bacteria. So really, if
you want to lose weight, you should just use antibacterial. So, yeah,
just get get rid of all of those, all those bacteria,
although you know, I mean, I'm sure they served the purpose,
(04:23):
but these all these microbes love to feast upon the
fatty sweat excreted by the apicron gland because they contain
something called a glycoprotein, which is a protein covered in sugar. Donut. Yeah,
so bacteria like nom nom nominal when we sweat sweat
(04:44):
donuts and sandwiches. That's that's really awesome. Um. Now, there
there's regular albio, which you know, and if you've ever
been to the gym or run or been outside on
a hot day, you've you've probably smelled yourself at some point.
You're like penny chick shower. But that's that's not really
a problem. Everybody's got bio everybody has a smell from
(05:04):
time to time, especially if you're not doing your laundry
or whatever. When it actually gets bad, it's called brom
hydrosis though, and that's the chronic condition in which excessive
odor emanates from the skin. And there's a bunch of
different health conditions that can cause you to smell anything
from just like excessive BO to actually having a fish smell.
It just kind of depends on health issues. Yeah. For instance,
(05:28):
um diabetes in particular is linked to BO. If you're
not monitoring your blood sugar and you have diabetes, you
can develop something called k o acidosis, which causes fruity
smelling breath and a pungent BO. Then also with thyroid problems,
if you have an overactive thyroid, the body might excrete
an excessive amount of sweat. It's interesting how how the
(05:52):
BO will will signal these internal issues going on. But
when it gets really bad, it's with this condition called trimethylaminuria,
which it's much easier to call it by its handy
acronym t M a U. It's when the body doesn't
break down this specific kind of amino acid properly, and
(06:13):
it causes a distressing fishy odor. Yeah. And the thing
is they tell you to avoid certain foods, but as
I was reading the list, I don't know what you
can eat because it says you have to avoid foods
like eggs, liver, seafood, beans, peanuts, broccoli, etcetera, etcetera. Like
there's a lot, there's a lot you cannot eat well.
And I'm sure for you, Caroline, eliminating the liver from yes,
(06:36):
I don't know liver sandwiches day in and day out
because you subsist off of cat food. Yeah, it's anything
that contains coline actually, And and again it's it reminds
me of our steliac disease episode where you have two
people with steliac haves to eliminate gluten, which is in
(06:57):
so much of of what we eat as well. Um,
And there was a two thousand eleven study speaking of
T M a U out of the monell Chemical Sensus
Center that found that a third of patients with an
unexplained odor who had that fishy odor that's you know,
that actually starts to affect like different areas of their life,
socialization and psychology because they have the smell, they don't
(07:18):
know what's going on. And they found that you know what,
the unexplained odor, it's the t m au. So if
you got a fishy smell going on out there could
be could be that the body doesn't processes amino acids. Yeah. Well,
there's also an effect that your diet has. We mentioned
diet meat meat. If you're a meat eater as I am,
(07:42):
apparently you don't smell as good as vegetarians. Yeah. This
was from a study called the Effect of Meat Consumption
on Body Odor Attractiveness that was published in the journal
Chemical Sense in two thousand six. Now, this was specifically
male meat eaters, and they had thirty women who were
not on any kind of hormonal contraception, which is important because,
(08:05):
as we've talked about before, birth control might tinker with
women's sense of smell. But they found that at least
among these thirty women, these smells of men who were
not or on a non meat diet were more pleasant, yeah,
less intense, significantly more attractive. So if you're looking for
(08:28):
a reason to go vegetarian, I guess these thirty women
would really appreciate it. Um. There's also if you want
to avoid just your run of the milby. Oh, you know,
they talk about strong smelling food like curry, spices, and
spicy food, because those actually do. Spicy foods increase your
body temperature. I mean, if you've ever eaten something super spicy,
you know you start to sweat. I'm a wolf and
I can't eat spicy food, so that's not a problem
(08:50):
for me. The problem for me happens to be garlic.
Not that I eat it all the time. I'm you
know whatever. I'm not trying to ward off any vampires
or anything, but onions and garlic are a volatile sulfur,
a substance, so look out for that. You can you
can smell back. Yes, we will excrete those smells through
all of those those pores on our body. Um. But
(09:13):
the thing is, you know, we we all have this
distinct bio whether or not it's amplified by something, you know,
condition like T M A U. Or for me, my
love of garlic and onions, I do cook with them
excessively lips uh. But you know, the thing is we
do so much to mask our own body odor. For instance,
(09:35):
there's a study which found that sevent of women and
sixty pc of men use a deodorant every day, while
forty percent of women also use it perfume every day.
We're just coding ourselves in sense. I wonder if that's
like a really American thing though, Like I feel like
that's very American to try to wash everything off of
(09:57):
you and not smell like your natural self. Because my friend,
her husband is from England and he doesn't use any
theater and he doesn't smell. Yes, there are differences among
like the body oder preferences by culture. So and I
have a feeling this was published in the Review of
General Psychology and it probably was from a Western study sample.
But let's get more into these unique smells that we have,
(10:21):
because you know what I'm all about, embracing our own
I mean, keep it, keep it under control, but embrace
your your your scent, your unique scent. Sure well, you
could call it your your fingerprint smell, or your odor
print or your scent print, if you will. The Journal
of the Royal Society interface in April two thousand seven,
(10:42):
researchers tested armpit, sweat, urine, and saliva from about two
hundred adults and found that the most volatile compounds were
actually in sweat, meaning that that had the strongest smell,
and they found and they were looking at it. They
found individually distinct fingerprints and a re producible difference between
the sexes. Yeah, they're referred to as genetically determined odor types. Um.
(11:08):
And there's another study which has found that you can
actually sniff out relatives in a way because of those
genetic links with your odor. Your relatives do kind of
all all smell similarly, which I can find fascinating. Yeah,
I don't go around. Maybe I should smell my mom more.
I don't know. Yeah, it's gonna make for some awkward
(11:29):
family or union moments, but you should do it. Thanksgiving,
you're going around just sticking your nose and people's necks
once they're taking their turkey naps. You just sneak up.
Yeah that Yeah, that makes for awkward hugs like, oh,
it's so good to see you uncle. Any Like, wait
a minute, you don't smell like me. Well, that whole like,
(11:49):
that whole constant that either genetic factor or that that
family factor that that seems to run. Um, it doesn't
change even if you change your diet. You know, we
talked about uh, spicy foods or garlic and onions. But
the Monell Center in October two thousand eight found that
an individual's underlying odor signature that that sounds nice is
(12:10):
still detectable even when they're major dietary changes. And they
also they use the term odor print. They say that
we have a consistent odor print, just like a fingerprint.
And it's not so surprising that we have the specific
odor prints because, as we've mentioned before, UM, scent is
one of the ways that we in humans instinctively UH
(12:33):
can determine someone's major histo compatibility complex in other words, UH,
their genetic difference to us, because if we a lot
of times, the people that smell the most attractive to
us have the most diverse major historic compatibility complexes, which
would mean that our offspring would have a better chance
(12:55):
of survival because you know, we want to avoid avoid inbreedings.
We're totally hurting the future of the human race, and
we put on deodora. That's what I'm hearing. Possibly it's true.
But let's get more into gender and sexual orientation, because
there have been a ton of studies UM around scent preferences,
and UH it's really interesting. For instance, UM, in one study,
(13:18):
straight women prefer the scent of dominant men, especially when fertile.
That's one. That's one of those studies where I wanted,
you know, like shake my fistic science a little bit fertile.
Do they use the word fertile fertile? Oh? Yeah, and
we uh. Straight women also tend to prefer the scent
of men with more symmetrical bodies. I can, I can
(13:42):
smell the shape of you. But at the same time, though,
there was another study out of the Archives of Sexual
Behavior from two thousand seven which found that I believe
this is also straight women again preferred the smell of
gay men's T shirts over straight men's T shirts. Yeah,
(14:04):
they had T shirts from gay men's, straight men and
just out of the package, like just off the rack,
and it was rated as like gay means were up
at the top, followed closely by out of the package
t shirts as far as like pleasant pleasantness goes, and
then straight men's T shirts came way behind. So you
hear that guy, straight duds out there, you kind of stinky. Well,
(14:28):
there was a there was an earlier study from the
Monell Center that they do a lot of smell research
over there. Good for you guys. Um, they had a
gay and straight men and women make preference judgments on
T shirts again. You know, you'd wear your T shirt
around and kind of get it all stinky and people
would judge it. Uh. They actually found a gay men
(14:48):
preferred odors from gayman and heterosexual women. So there you go.
Everybody has a preference, and it seems that women in
particular are maybe more a tune to this scent thing
than men might be. Uh. There was a survey published
in the journal Evolution and Human Behavior in two thousand
(15:09):
two which found that college women ranked body odor is
more important for attraction than looks or any other factor
except pleasantness. And what are the guys right as the
number one thing? Yeah, they looks as most desirable. Um,
and even in childhood there seems to be that gender difference. Uh.
(15:30):
This is from developmental psychology from two thousand three. They
had children and adolescents smell various odors and raithed them
for how much they liked it, and only the girls
disliked male sweat and could identify it. Yeah, And they
did a follow up experiment where they cued everybody into
the identity of the odors and then, regardless of gender,
(15:52):
adolescents over children disliked male sweat. More so they think
that maybe there's some sort of like social thing that
once you get older, you're like, oh men, men, sweat
that's dirty unless you're fertile and he's dominant apparently in
your a heterosexual fifty shades of uh oh. But speaking
(16:15):
of UM, I thought this was pretty fascinating. There was
an article published in May two thousand twelve in The
New Scientists by Mary McLoud all about scent and um
all of the most contemporary research about it, and she
cited a study out of Poland which found that participants
could by simply smelling people's sweat predict their personality type,
(16:40):
for instance, whether or not they were a little more
neurotic or extroverted. Um. Yeah, I mean the little more
pungent people were a little more erotic, but not erotic
neurotic or you know, maybe that was tested too, very
erotic sweat, um, But I thought it was It was
(17:01):
interesting that even even with personality, win for so much
from someone's scent, including their age. This is some of
the most recent research to come out, and this is
again coming from the Manel Chemical Senses Center, and they
were looking into this. The old stereotype about old people
(17:24):
smell for lack of better phrasing. Yeah, people tend to
find old people smell to be gross and off putting
and negative, and they don't have anything nice to say
about it. But that they think because the study that
might have more to do with the context, because they
didn't tell people necessarily that it was an elderly person
who had donated the smell. They just had all these
(17:47):
smells that they were testing, and the subjects managed, though,
to separate out the smells that belonged to the elderly.
They didn't, however, think they smelled bad or nasty or
off putting. They said that they smelled more pleasant than
the rest of them. Yeah. They had the participants divided
up into age groups and um by sex, and the
(18:09):
group that consistently smelled the worst. Guys, I'm really sorry
to keep keep on calling you out here, just stating
the facts. Middle aged men, you were the stinkiest lot.
But elderly men in particular, even more so than the
elderly women, had the most pleasant and almost non existent smell. Yeah. Well,
(18:34):
they point out that that might be because elderly men
have lost testosterone, so things are evening out in the
hormone area. But I thought, you know, like we have
we have this association I think with you know, it
goes along with nursing homes and retirement homes and those
very particular smells that are there, and once you remove
(18:56):
the older person from that context, and we kind of
this is so C eight the old people smell is
actually kind of figment of our imagining, at least in
a negative sense. Well, and the participants who donated donated
their scent. Uh, we're healthy, so there wasn't an issue
of any like health issues that might have been contributing
(19:16):
to a bad smell for instance. And this does that
that study from the Monnel Center does support a previous
study published in the Journal of Investigative Dermatology from two
thousand one, which found a specific component that's characteristic of
the body owner of the middle aged and senior citizens.
(19:36):
And they think it has to do something with changes
in our bodies in mono unsaturated fatty acid compositions of
our skin surface lipids. Yeah, quote unquote the deterioration of
the body owners for the middle aged and the elderly.
That's a nice way to put it. So like, so
are diminishing body grease? Yeah, basically, well, let's go to
(19:59):
somebody who's not greasy. That's babies. That's maybe the best
podcast transition ever been made. Well, Um, this this is
an interesting study. Uh, this is hormones and behaviors. New
moms are more attracted to the body odor of newborn
infants than are non mothers, even when they didn't know
(20:21):
the source. It's like they just like smell freshly baked
cookies and just go for it. It's like, I smell
something that needs nurturing in this room, a baby in
this room. Um. And they did find that mothers with
higher cortisol levels are better able to recognize their own
infants smells. Yeah, and it's a it's a two way
street too, because by two weeks, infants can distinguish between
(20:44):
their mother's breast milk and that of another mother and
they that's one of the quickest bonds to happen between
a mother and a child. Is that intense the baby
bonding to the mother smell and vice versa. Yeah, it's
really surprising how quickly infants developed that strong sense of smell.
I mean, they can't see very well and they certainly
can't tell you what's wrong. If they're crying, but they
(21:05):
can smell you, all right. Yeah, so yeah, familiar smells
they can soothe infants. You think about that, I mean,
if you think about it, like the the that intense
link between our old faction and memory and how that
you know, there's that tight um association in the brand.
I'm sure our sister or Brother podcasts Stuff to Blow
(21:27):
your Mind has done lots on the science of smell.
But just to finish things off with this smorgess board
of smells podcasts, let's talk about something called old factory
reference syndrome, which I had not heard of before you
(21:47):
sent me some info about it, Caroline. Yeah, I had
never heard of this, but you know, there's there's you
can be self conscious about the way you smell, Like
if you've been outside running around, you might be like, oh, gosh,
I hope I don't smell too bad, especially you know,
if you have to go back in to work or whatever.
But it's usually not debilitating. But there are people with
olfactory reference syndrome who feel that they smell so bad
(22:09):
that nobody would actually want to even spend any time
with them, be in the same room with them at all.
And these people usually fall into depression and shut out
the world. And this is from Catherine Phillips, who's a
psychiatrist at Red Island Hospital. They found that sixty of
these people have thoughts of suicide and thirty two percent
actually attempted. And they spend these people can spend somewhere
(22:31):
between three and eight hours a day obsessively thinking about
their various odors that nobody else can smell. So you're
sitting there constantly just in a state of high alert
like panic, thinking like, oh my god, you can smell
my feet. Can you smell my feet? You can totally
smell my feet. Well, a majority thought seventy thought that
the smell was from their breath, and then sixty percent
it was armpit smell, and thirty five percent thought the
(22:52):
odors were coming from their genitals and um. The doctors
think that at first they thought it was something to
do with ski staphrenia, but now they are seeing more
of as a link to O c D behavior. Yeah,
and so they usually try to treat it with cognitive
behavior therapy but also exposure therapy. So, no, you're going
(23:12):
to eat those onions and garlic and then you're gonna
go out and you're gonna socialize with people, darn it,
and so hope with the hope that that can actually
help them get over it. But even in the general population,
there is a link between heightened anxiety and a more
acute sense of smell, which is kind of fascinating and
(23:33):
and reminds me of our you know what animals we
are sometimes. Yeah. This was a University Wisconsin study in March.
They put a bunch of people in m r I
machines and and tested basically what happened in their brain
with the smell region of their brain and when they
were anxious. And they found that as anxiety arises, so
(23:55):
did the subject's ability to discriminate negative odors. And they
think that it is goes back to our evolutionary roots
of you know, threat detection and all of our since
that's going on high alert to keep ourselves safe. Oh
my god, the prairie tiger is going to kill me.
Somebody farted runway. Uh So I think that's all the
(24:18):
smell research that we have. Um My takeaway is, you know,
if a straightman smells very good, uh, maybe he might
be gay or very dominant, or a vegetarian or a
vegetarian all of these who doesn't eat spicy food or garlic? Indeed? Uh,
(24:41):
lots lots of fascinating takeaways. Oh, I've got one more
I forgot to mention. This was also from two thousand
and twelve in the Journal of Forensic Science. They found
that like police dogs trained dogs, Caroline, they are better
at sniffing out women than men. Well that's just not fair,
So lady criminals also be aware watch out. So that's
(25:07):
all we got, uh, Since b O any any BO
related stories we would like to hear from you listeners now,
Mom Stuff at Discovery dot com is where you can
send us your letters, and we got a couple here
to share with you. This one is from James. The
(25:30):
subject line is exciting fiction. Exciting isn't quote? So who
knows what he has in store for us? He says,
I'm a classicist and I thought i'd share some fun
facts about a it and the ancients when it comes
to exciting literature. The ours Amatoria comes in three books.
The first is for guys and teaches you how to
get a girlfriend. There's some really cute scenes, like how
to help your lady friend have a good time at
(25:51):
the horse races. That's my main concern, thank you. The
second is for ladies, teaching them how to get a boyfriend.
The third teaches you how to break up. We don't
know why Ovid was exiled. It's even possible that he
never was, and his poetry on the subject might be
some weird performance piece like what Joaquin Phoenix tried to
pull a few years ago. That's weird, and Netflix keeps
recommending that I watched that movie and I don't want
(26:12):
to um Appleus is Metamorphosis is a very funny, erotic novel.
It's mostly from the main character's perspective. He gets turned
into a donkey early on and stays that way almost
to the very end. The Greek novel is a genre
that's more like your modern day romance novel, with two
young lovers, pirates, kidnappings, fake death, et cetera. On the
(26:33):
visual side, he says, if you ever took a mythology
course or Roman sive, you probably saw some Pompeii and
frescoes of pre APUs, a Roman fertility deity with a
comically large fallace uh second bullet point. Greek base painting
from the classical period sometimes depicts graphic acts with the
characters fully disrobed. I'm not sure who would want their
olive oil shipped in that, but hey, different strokes and
(26:54):
all that. So thank you for the the saucy fiction
pointers Erotica. It's been around for agels. Well. I have
an email from Dima in Pakistan and this is in
response to our episode on donating old clothes, and she
has some pretty nep few ways that she deals with that.
(27:16):
She writes. My best friend's mom and I are usually
the people UH folks come to when they want to
donate something, especially clothes. So what we do first is
sift through them and separate them into two piles, horribly
ugly clothes slash unusable clothes and clothes people might actually want.
With the horrible clothes, I cut them and tie the
(27:36):
strips together until it forms something like a ball of
yarn for each item. With that yarn, my best friend's
mom will crochet a rug in about three hours while
she watches TV or something. She gives these rugs away
to anyone who wants them, and we plan on selling
some next year at our city's heritage festival. With the
usable clothes, we have created a swap with our friends,
(27:57):
which I'm making many people come to. So that's two
great ideas for clothing donations. And if you have any
great ideas or stories or just a hello to share
with us, you can send us an email mom Stuff
at Discovery dot com. You can find us on Facebook,
and you can follow us on Twitter at mom Stuff Podcast,
(28:20):
and you can check out our blog. We're on Tumbler now, folks,
that is stuff Mom Never told you dot tumbler dot com.
And as always, you can make yourself smarter by heading
to our website, It's how stuff Works dot com for
more on this and thousands of other topics. Is it
how stuff works dot com. Brought to you by the
(28:47):
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