Your choice of deodorant may affect your social life. But did you know it may also impact the microbes in your armpit?

New research finds that the antiperspirant or deodorant you wear can affect the type and quantity of bacteria that live in your underarms. Researchers at North Carolina State University, the North Carolina Museum of Natural Sciences, North Carolina Central University, Rutgers University and Duke University looked at 17 participants — seven who used antiperspirants, five who used deodorants, and five who used neither product. The results of the study were published in the journal PeerJ.

Participants' armpits were swabbed daily as they followed their normal hygiene routine for one day, then didn't use any product for five days, then used antiperspirant for two days.

Researchers cultured all the armpit samples to see what microbial organisms were growing on each participant and how they changed from 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,” said Julie Horvath, head of the genomics and microbiology research laboratory at the NC Museum of Natural Sciences and co-author of the paper, said in a statement. “In addition, people who used deodorant actually often had more microbes, on average, than those who didn’t use product.”

By day three, participants who had used antiperspirant were beginning to see more microbial growth. And by the sixth day, the amount of bacteria for all study participants was nearly the same.

“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 said.

The researchers didn't say whether having an impact on the armpit's "bacterial community" was potentially harmful or could possibly even be beneficial.

“Using antiperspirant and deodorant completely rearranges the microbial ecosystem of your skin — what’s living on us and in what amounts,” said Horvath. “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.”

Mary Jo DiLonardo covers a wide range of topics focused on nature, health, science and anything that helps make the world a better place.

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