Antiperspirant alters the microbial ecosystem on your skin

February 2, 2016
skin
Human skin structure. Credit: Wikipedia

Wearing antiperspirant or deodorant doesn't just affect your social life, it substantially changes the microbial life that lives on you. New research finds that antiperspirant and deodorant can significantly influence both the type and quantity of bacterial life found in the human armpit's "microbiome." The work was done by researchers at North Carolina State University, the North Carolina Museum of Natural Sciences, North Carolina Central University, Rutgers University and Duke University.

"We wanted to understand what effect antiperspirant and have on the that lives on our bodies, and how our daily habits influence the life that lives on us," says Julie Horvath, head of the genomics and microbiology research laboratory at the NC Museum of Natural Sciences, an associate research professor at NC Central, and corresponding author of a paper describing the work published in the journal PeerJ. "Ultimately, we want to know if any changes in our are good or bad, but first we have to know what the landscape looks like and how our daily habits change it."

"Thousands of bacteria species have the potential to live on human skin, and in particular in the armpit," says Rob Dunn, a professor of applied ecology at NC State and co-author of the paper. "Just which of these species live in any particular armpit has been hard to predict until now, but we've discovered that one of the biggest determinants of the bacteria in your armpits is your use of deodorant and/or antiperspirant."

"Within the last century, use of underarm products has become routine for the vast majority of Americans," says Julie Urban, co-author of the paper, assistant head of the genomics and microbiology laboratory at the NC Museum of Natural Sciences, and adjunct professor of entomology at NC State. "Yet, whether use of these products favors certain bacterial species - be they pathogenic or perhaps even beneficial - seems not to have been considered, and remains an intriguing area needing further study."

To learn about the microbial impact of antiperspirant and deodorant, the researchers recruited 17 study participants: three men and four women who used antiperspirant products, which reduce the amount we sweat; three men and two women who used deodorant, which often includes ethanol or other antimicrobials to kill off odor-causing microbes; and three men and two women who used neither product. They then launched an eight-day experiment, in which all of the participants had swabs taken of their armpits between 11 a.m. and 1 p.m.

On day one, participants followed their normal hygiene routine in regard to deodorant or antiperspirant use. On days two through six, participants did not use any deodorant or antiperspirant. On days seven and eight, all participants used antiperspirant.

The researchers then cultured all the samples to determine the abundance of microbial organisms growing on each participant and how that differed day to day.

"We found that, on the first day, people using antiperspirant had fewer microbes in their samples than people who didn't use product at all - but there was a lot of variability, making it hard to draw firm conclusions," Horvath says. "In addition, people who used deodorant actually often had more microbes - on average - than those who didn't use product."

By the third day, participants who had used antiperspirant were beginning to see more microbial growth. And by day six, the amount of bacteria for all study participants was fairly comparable.

"However, once all participants began using antiperspirant on days seven and eight, we found very few microbes on any of the participants, verifying that these products dramatically reduce microbial growth," Horvath notes.

The researchers also did genetic sequencing on all of the samples from days three and six, to determine how antiperspirant and deodorant might affect the microbial biodiversity - the composition and variety of types of bacteria - over time.

They found that, among who hadn't worn deodorant or antiperspirant, 62 percent of the microbes they found were Corynebacteria, followed by various Staphylococcaceae bacteria (21 percent), with a random assortment of other bacteria accounting for less than 10 percent. Corynebacteria are partially responsible for producing the bad smells we associate with body odor, but they are also thought to help us defend against pathogens. Staphylococcaceae are a diverse group of bacteria that are among the most common microbes found on human skin and, while some can pose a risk to human health, most are considered beneficial.

The participants who had been regular antiperspirant users coming into the study had wildly different results. Sixty percent of their microbes were Staphylococcaceae, only 14 percent were Corynebacteria, and more than 20 percent were filed under "other" - meaning they were a grab-bag of opportunistic bacteria.

"Using antiperspirant and deodorant completely rearranges the microbial ecosystem of your skin - what's living on us and in what amounts," Horvath says. "And we have no idea what effect, if any, that has on our skin and on our health. Is it beneficial? Is it detrimental? We really don't know at this point. Those are questions that we're potentially interested in exploring."

The new findings also highlight how human behavior can have a profound, if unintended, impact on the evolution of microbial organisms.

In another paper, published last month in Proceedings of the Royal Society B, the researchers, in addition to collaborators at Duke and the University of Pennsylvania, examined the diversity and abundance of microbes found in the armpits of humans, compared to other primates: chimpanzees, gorillas, baboons and rhesus macaques. In that paper, the researchers found that armpit microbes have evolved over time in conjunction with the primates they live on. But the microbial ecosystems found in the armpits of humans are vastly different - and far less diverse - than those found in our primate relatives.

"One exciting finding was that the non-human primates were more covered in fecal and soil associated microbes, which we often view as dirty," Horvath says. "Perhaps the diversity of fecal and soil microbes on non-human primate skin serves some benefit that we don't yet understand or appreciate.

"Over evolutionary time, we would expect our to co-evolve with us," Horvath says. "But we appear to have altered that process considerably through our habits, from bathing to taking steps to change the way we look or smell."

Explore further: Human immune system shapes skin microbiome

More information: Julie Urban et al. The effect of habitual and experimental antiperspirant and deodorant product use on the armpit microbiome, PeerJ (2016). DOI: 10.7717/peerj.1605

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ogg_ogg
1 / 5 (1) Feb 02, 2016
So, according to these "researchers", their goal was to determine "... if any changes in our microbial ecosystem are good or bad..."
Yeah, "good" and "bad" are rigorously defined scientific terms. See, the world is binary; a thing or a person, a process, a system, or a culture or religions are either "good" or "bad". Wow.
adam_russell_9615
5 / 5 (2) Feb 02, 2016
I think the actual point of deodorant is to prevent the multiplication of the bacteria that produces bad smell. Its not you that smells bad, its them. Otoh, I think its a bad idea to prevent perspiration itself. You sweat for a reason. Blocking pores is bad.
NIPSZX
not rated yet Feb 02, 2016
Funny how everything that the human race invented in the last 100 years has turned out to be bad now. Fast food hamburgers were the rage in the 60s and 70s because it was easy food and filling. Now it is the worst thing you can eat. Processed food was also created in the last 100 years to withstand spoiling and now processed food is considered to be bad due to the chemicals that help the food withstand going bad. Deodorant is also in this category. It was developed to help curb body odor and now we are realizing the body odor has helpful bacteria that help ward off disease. Pesticides are also in this category, pesticides were created to help keep pests and bugs from ruining the crops grown for food and now it turns out they are bad for human consumption also. It is funny how all these great inventions, at one time, have turned out to be negative after research.
UFOJoe
not rated yet Feb 02, 2016
This article seems to categorize deodorant and antiperspirants as one in the same. As a blue collar worker I have to sweat, yet I do not wish to smell. Use of deodorants and avoiding antiperspirants always has worked well. When your body needs to sweat and is blocked all the moisture goes to your feet causing nasty problems with footwear.
eric_in_chicago
not rated yet Feb 06, 2016
Uncontrollable Foot Odor, Joe?
Multivac jr_
not rated yet Feb 07, 2016
It'd be nice to find out how those deodorant 'rocks' (basically a chunk of various salts) affect it, too.

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