It’s the Pits

**Today we have a guest post from Dr. Julie Horvath, Director of the Genomics & Microbiology Research Laboratory in the Nature Research Center, the new wing of the NC Museum of Natural Sciences.**

As a primate comparative genomicist I study primate DNA sequences and compare them to humans and other non-human primate DNA sequences. I am very interested in connecting how changes in DNA sequence (genotype) can alter a human or animal’s outward appearance or characteristics (phenotype).  Many of my research projects focus on connecting DNA sequence changes with behavior, anatomy, and ecology.

Photo Credit: Divine Harvester, Flickr

When I met Rob Dunn, I never dreamed I would be excited about starting a project where I was swabbing people’s or non-human primates’ armpits to collect their smelly microbes.  Yet today we are doing just that. When you pass by my Genomics & Microbiology Research Lab on the third floor of the Nature Research Center you’ll see a white board listing the members of the lab and what they work on. When you read that someone studies “armpit biodiversity” you might think to yourself, “Who drew the short straw on that research project?”  But soon you may start asking, “How do I get involved in that cool project?!”

We (the scientific community) have recently learned we have more microbial cells living on us and in us than human cells. There are pounds of bacteria living on our skin, in our guts, ears, and noses. Many of these bacteria are beneficial, and it is only occasionally that harmful bacteria cause problems. The Human Microbiome Project is working on characterizing all of the microbial species that live on and in us in order to better understand how we interact with and benefit from these microscopic travelers.

When talking about armpits, it turns out that it isn’t the person or animal that has an odor, it is the bacteria living on the person or animal that produces the odor. We know that people and animals choose mates based on smell, so we are actually basing some of our behaviors (e.g. mate choice) on these tiny microbes. This is intriguing since smell is also correlated with expression of some immune system genes. Therefore, investigating armpit microbes may be one way to connect particular gene sequences with behavior and mate choice. We’re interested in learning how people’s daily habits people influence the bacterial species hitchhiking on them. And longer term we plan to examine multiple non-human primate armpits for a comparison of the bacterial species living on them and us.

Here's a rich bacterial plate grown from a belly button swab. Mine was devoid of any bacteria.

Several months ago, a few of us in the Lab swabbed and plated our skin microbes, mostly to get a few pretty demo plates for the NRC Grand Opening. Our collaborator Rob Dunn and the Your Wild Life team had piqued our interest in their Belly Button Biodiversity project and so we swabbed both our belly buttons AND our armpits. Everyone’s plates had hundreds of bacterial colonies…except mine. Nothing grew on my belly button or armpit plates.  I thought to myself: “Is something wrong with me?” This is where most people would probably be happy that they didn’t have microbes growing on them, but as a scientist I was concerned that something was wrong with me. I went to my dermatologist shortly after the “no growth” incident, and I asked if I could have some skin problems because I didn’t have any microbes growing on my skin. He looked at me like I was crazy. So I set out to figure out what was causing no bacterial growth on my agar plates. In sampling more people we noticed that there were others who also failed to grow any bacteria on their armpit plates. In true science fashion, we started an experiment.

Let’s take one man (fellow co-worker) and one woman (me) who wear antiperspirant every day. Swab their pits and see if anything grows. Then tell them to stop wearing antiperspirant and swab them every day to see how long it takes for bacteria to grow. I did this for 5 days. And boy was it hard to go antiperspirant free for that long — especially on the days I had to talk to give public talks in the Daily Planet Theater. But weirdly enough, after about 5 days I got used to being antiperspirant free. So I continued the experiment until I got to 12 days sans antiperspirant. What we noticed was that I had very few bacterial colonies growing on plates from early samples, but as more days passed without antiperspirant, more bacteria started to grow on my plates. This suggested that antiperspirant inhibits bacterial growth. Unfortunately, my fellow co-worker joining me in this experiment did not see an even increase in his bacteria growing over time. And one can’t make any solid scientific conclusions from a sample size of two. We determined that we needed a larger study with more people and more consistent sampling. And so our pilot study begins….

Follow our experiment in-progress (as well as the trials and tribulations of the 18 volunteers we recruited to go without antiperspirant or deodorant for an entire week in the hot North Carolina summer!) here on the Your Wild Life blog and via Twitter (#PitStart).

Dr. Julie Horvath is the Director of the Genomics & Microbiology Research Laboratory in the Nature Research Center, the new wing of the NC Museum of Natural Sciences.

The Armpit Project is a collaborative project involving Drs. Rob Dunn and Holly Menninger in the Biology Department at NC State University (Your Wild Life Program), Dr. Jul Urban, the Assistant Director of the Genomics & Microbiology Research Laboratory, and Dr. David Kroll, the Director of Science Communication at the Nature Research Center.

By |2016-11-22T13:47:33-05:00August 27th, 2012|

About the Author:

Holly Menninger
As Director of Public Science, Holly coordinates our empire of citizen science projects and manages the online science communication here at Your Wild Life. An entomologist by training, she’s a science communicator by passion and practice.


  1. Avatar
    Karen August 27, 2012 at 10:09 am - Reply

    Another interesting topic related to bacteria growth is that people who have had radiation therapy to their arm pits (research radiation to the mantle field) will no longer secrete sweat or grow hair under their arms. So- maybe one day instead of having to use deodorant every day there will be a one dose of underarm radiation treatment -specifically designed or tailored to that area and people will be free of sweat, hair and bacteria growth under their arms for the rest of their lives.

    • Avatar
      Daniel C. November 15, 2012 at 2:16 am - Reply

      That sounds horrible. This is just simply a part of our human body. Unfortunately our current and very recent cultural norms would like us to rob all natural aspects of the armpit and find way to make it effectively disappear.
      Lets stop shaming ourselves for have a body and instead embrace it fully.

  2. Avatar
    Beatriz Moisset November 7, 2012 at 8:19 pm - Reply

    Somewhat related to Karen’s comment, after lymph node removal, 13 years ago, I noticed very little or no sweat on that armpit. Would the microbial fauna change after that surgery?

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    valerie summer November 10, 2012 at 8:19 am - Reply

    I have been concerned about the use of chemicals on and in our bodies since forever. As we know, bo is caused not by the sweat we produce, but by the bacteria that grows in the warm and sweaty places. Also, sweating is a normal bodily function that cools the body. Therefore, about ten years ago I decided I would quit using anti-perspirants and simply wipe my armpits with alcohol each morning after my shower. I also decided to apply the alcohol to my stinky feet at the same time. Well, a simple wipe immediately turned to liberal drenching of both my feet and armpits, and neither has smelled since then. My poor friends and relatives are constantly being asked to sniff me and tell me if I smell bad. So far, no smell. Also, I initially feared my pits would dry out or become flaky, scaly, or irritated. Nope – the skin is just fine. Yes, I sweat; no, it doesn’t smell bad. By the way, I live in Florida.

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    Rick December 14, 2012 at 7:25 am - Reply

    Shaming ourselves for having a body??? Science, such as gathering info like these people do, makes your life better.
    No one is asking me to rob my “natural aspects of the armpit” Thanks for the laughs!!!

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    Eileen March 4, 2013 at 9:44 am - Reply

    I use mineral salts because the aluminum in most antiperspirants is a known thyroid inhibitor. Since I am already hypothyroid, I try to be aware of chemicals that will have a deleterious effect on my already suboptimal thyroid producing gland. What I have found is that minerals salts work surprisingly well at keeping bacteria growth in check. Even when forgetting or missing a day, odor is not present.
    Of course, now I wonder if keeping that bacteria growth in check is causing some other problem :-(

  6. […] appearance or characteristics, for which she enlists museum visitors in a very unique way. By inviting members of the public to let museum staff swab their armpits and bellybuttons for cell cult…, Horvath is studying the bacteria that grow on our bodies and how our behaviors affect these […]

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    "Dirty Emilie" September 21, 2013 at 3:00 pm - Reply

    I stopped wearing anti-perspirant and using more natural products nearly 10 years ago after learning that I had a small brain tumor. I used to also work in finance and investments and run around in hot suits in summer and sprint between airline terminals. Now, after doing a career transition, I work full time as a backcountry guide and run my own adventure travel business. Throughout all of the years and all the sweaty situations, there have only been a handful of times when I and others could tell that I really smelled more than those around me. I’ve saved tons of money on laundry detergent and dry cleaning because I don’t have to wash off deodorant stains, and overall I feel more peace of mind for letting my body do it’s natural thing. Looking forward to more of your results!

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    rita August 6, 2014 at 5:10 pm - Reply

    I took a bath with bleach to moderate some of the bacteria in our water supply last week. I am here to report my BO increased.

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