Deodorants and antiperspirants might be part of your daily routine to fend off odors and sweat, but they do more than affect your confidence. They actually change the microbial ecosystem of your skin.
Researchers from NC State, Duke University, Rutgers University, North Carolina Central University and the North Carolina Museum of Natural Sciences collaborated together to understand how deodorants and antiperspirants affect the kinds of microbes that live in the human armpit.
Julie Horvath, a research associate professor at NCCU and head of the Genomics and Microbiology Research Lab at the North Carolina Museum of Natural Sciences, is a member of the research endeavor and described that its beginning was to engage students and museum visitors.
“Because we want to not only engage students but also engage museum visitors in research, science and the scientific process — that’s kind of how this project began,” Horvath said. “Rob Dunn [an author of the study and ecology professor at NC State] had been studying belly buttons on people, and we started thinking about how we could engage visitors. We asked if we could continue with belly buttons, but it might be fun to try a new area of the body.”
To carry out the study and find differences in people’s underarm microbes based on hygiene product use, a group of willing participants was split into smaller groups of deodorant-only use, antiperspirant-only use and no-product use. Over the course of eight days, product use was changed and the armpit areas would be swabbed to look at the microbes each day.
“We enrolled people from the museum, and visitors, to try and do this study look for an ecological time point and see, ‘well if you usually wear product and you stop wearing product, how many days does it take for there to be enough microbes on your body so that you look similar to someone who never wears product,’” Horvath said.
The microbial cultures would be grown for a few days to see their development and the variety of bacteria. According to Horvath, sequence-based analysis was also used since not every microbe on the body will grow in the lab. This approach uses DNA sequences to identify bacterial species.
The researchers found that bacteria samples from regular antiperspirant users two and five days after stopping product use were more diverse than that of deodorant users and users of no product.
This study presents a measured difference, rather than benefit versus non-benefit of the microbial changes. However, variation or diversity of microbes tends to seem healthier in other microbiomes.
“If we look at the gut microbiome and other parts of the skin, the more variation you have, typically that’s a healthier state,” Horvath said. “So when you get down to only one or a couple predominant microbes, a lot of times that can lead to these perturbations that cause a flare up or an issue from the predominant microbe. So having more variation and diversity could be potentially a better thing overall.”
While the bacterial variety is higher with the antiperspirant users after stopping product use, the bacterial growth and abundance went down, according to the study. With the deodorant users, this effect is modest, if there at all, which Horvath said could be because deodorant is more easily washed away while antiperspirants actually block the sweat glands and give the bacteria less food to grow.
Factors besides deodorants and antiperspirants also change the microbial ecosystem of our skin.
“There are a lot of different factors that play into which microbes live on us,” Horvath said. “The deodorant/antiperspirant seems to be actually quite a large player looking at the armpits specifically, but there are many other things that play a role … it’s just that a lot of them are sort of very tiny amounts.”
Horvath explained that some of the contributing factors could be your diet, your gender, how much you exercise and the other products you put on your body.
As human hygiene and sanitation practices have changed over the past couple hundred of years, the microbes that are living on us also have changed.
“We’re eliminating some of these microbes that we thought were negative for us, so some parasitic worms for example,” Horvath said. “We sort of eliminated those from our bodies, but if you look at a lot of the primates, a lot of the primates still have those in their bodies. So maybe they are at some level doing something beneficial.”
Therefore, according to Horvath, it is a possibility that if one can keep microbes at a low level, then they might actually do something beneficial to our bodies. Horvath said, for example, that there have been some indications that microbes are work with the immune system.
According to Horvath, gender seems to be a big factor as well as antiperspirant/deodorant in the armpits. Eventually Horvath said she would like to get at the question of whether or not these microbial changes are beneficial, but that is a long road ahead.
“Getting to ‘are deodorants and antiperspirants bad,’ there is a lot more information we would need to know before we would be able to say that with our research,” Horvath said. “Our current research doesn’t say bad or good, it just says different.”
