What does your armpit say about you? Museum exhibit takes a look

“The Secret World Inside You,” the North Carolina Museum of Natural Sciences’ current featured exhibit, takes a close look at people – a really close look.

Its focus is the human microbiome, the private ecosystem made up of the trillions of microbes that live in and on people. As part of the exhibit, there are portraits of the microbes of “hometown heroes” – close-ups of the tiny organisms that live in notable locals’ armpits. For this interview, The News & Observer correspondent Corbie Hill had his own armpit and ear swabbed for the same purpose.

The N&O caught up with Julie Horvath, head of the museum’s genomics and microbiology research lab, to find out what taking a closer look at a person’s microbiome tells scientists. In her own research, she doesn’t just limit herself to homo sapiens; recently, Horvath’s team swabbed the armpits of nonhuman primates to compare with human microbes.

Q: What do you learn from looking at a person’s microbes?

A: In general they are starting to tell us what lives on people and might be beneficial to people. We used to do a lot of culturing work and culture the microbes that lived on people. What can grow on your body is a lot more than what we can grow in a lab, and so by doing this culture work, by growing things in a lab, we didn’t see everything that was on you.

Q: Because you’re removing it from the ecosystem it lived in?

A: Because your body has sweat and other chemicals on it that you can’t really replicate in a petri dish in a lab, so you’re missing some of the stuff that it needs to grow. Some things grow really well in a lab, other things don’t.

By doing the studies now we’re actually looking at everything that’s on you to try and learn what is maybe healthy. So we know there is a lot of variation between different people. What does that variation mean? Is it based on your daily habits, is it based on what your genetics might contribute to allowing certain microbes to grow and not? We’re really trying to get a good idea of what grows on people and how does that relate to your health and well-being, how does that influence your behavior, things like that.

Q: How far along is that research? Is that a fairly new direction?

A: It is. Because of sequencing technologies, now we can look at everything that lives on you. What we can do is we can take (a microbe) sample and we can extract the DNA, so we take the DNA from the microorganisms on your skin and we now extract it so we have the DNA in a tube. And now we take a piece of the DNA from each organism and we can sequence a piece of it and we can compare that sequence to known organisms that are already in public databases.

Q: What are some early conclusions?

A: My research, specifically, was really looking at antiperspirant and deodorant use. We know there’s a lot of variation between people, but one of the things that contributes a lot to that variation is whether you wear product on your arms. People who wear product are changing really dramatically which organisms can live there. When you wear this product, you are eliminating the organisms from being on your skin.

Q: So the smell is from the organisms?

A: These organisms drink your sweat and then they release compounds called metabolites, which are just compounds from the metabolic process. Their excrement is basically these different metabolites. Some of them smell, some of them don’t. So then what a lot of people cue into is the ones that smell. That’s what gives you your body odor.

If you wear antiperspirant or deodorant, you are either killing the microbes so that they can’t live there, so they don’t produce body odor, or you are actually blocking your sweat glands. That’s not giving them food, so there are fewer things there because there’s no food source. Depending on what product you use, you might have slightly different organisms living on your skin.

Some of those microbes that you’re changing may influence your health and well-being. Maybe they influence how attractive you are to mosquitoes, because mosquitoes also cue into those odors on your skin. That’s one of the things we’re looking at.

If you wear deodorant or antiperspirant, you wipe out life under your armpits at least and potentially elsewhere on your body as you take a shower and that chemical washes down. And then, let’s say you stop wearing product because you went into the hospital or because you go camping. Now the organisms that grow back quickly are a lot of the different types of staph, and some of those are more attractive to mosquitoes. Some of those have negative health implications. If you wipe out life under your armpit, there’s not a protective barrier on your armpit skin anymore. If you did go somewhere and now a pathogenic organism lands there, now there’s nothing to compete with it for resources, so it’s going to be able to take over pretty quickly.

Q: Is there a middle ground where you can smell good but not wipe out these ecosystems?

A: There are a lot of companies now that have come out with these probiotic deodorants now that are compilations of various probable bacteria that can then grow on your skin and maybe don’t produce that same body odor. Now you’re using potentially beneficial microbes to replace the ones that produce odor and now they’re on your skin and maybe not harming you in any way. You’re not killing off your good life, too.

I can just say, if you wear deodorant or antiperspirant, the microbes under your armpit look different than if you wore no product at all.

This story was originally published January 20, 2017 at 8:00 AM with the headline "What does your armpit say about you? Museum exhibit takes a look."