Deodorant and Antiperspirant Literally Change the Bacteria That's in Our Armpits

Deodorant is usually considered a necessary part of human existence (at least, our human existences). But according to a study, excessive deodorant and antiperspirant use is altering the microbes that live on your skin.

The study, published Tuesday in the journal PeerJ, tested 17 men and women, some of whom wear deodorant, some of whom wear antiperspirant and some who don't wear either. For eight days, they regularly tested and analyzed the microbiome that exists in their armpits, which include all sorts of bacteria, viruses and fungi. (Sounds fun, doesn't it?)

The test was to see if the different products literally changed the kinds of bacteria in people's armpits — and the clear finding was it did. There was, the researchers found, "a strong effect of product use on the bacterial composition of armpits," evidenced when people stopped using one product or changed to another.

So what do these ever-changing, gross-sounding specks mean for our armpits? Well, certain bacteria accomplish certain things, so we might not want to change them too much. By preventing our glands from producing sweat, in some cases, we end up starving these nice bits of bacteria. Think of those little glass memory balls from Inside Out and then picture all those balls slowly turning blue rather than yellow.

Using more deodorant and antiperspirant was found to increase staphylococcaceae, while those who used less or no deodorant at all had far more corynebacteria — which is the culprit for our smelly armpit odor, but is also benevolent and helps defend our bodies from harmful bacteria.

Overall, lead researcher Julie Horvath said in a statement, "people using antiperspirant had fewer microbes in their samples than people who didn't use product at all."

Which, y'know, sounds a bit scary. Meanwhile, a 2014 study found that using antiperspirant actually caused an increase in corynebacteria, which "could lead toward an altered, more unpleasant, underarm odor," study leader Chris Callewaert told the Washington Post.

"Wearing a product does affect the microbes under your arm, but what those short and long-term consequences are, we don't really know yet," Horvath told Quartz.

So we may or may not be getting smellier — it's fear of the unknown, basically. Maybe Matthew McConaughey, an actor known to not wear deodorant at all, has been right all along. Or maybe we should just follow our Teen Spirit and keep slathering it on like Katy Perry.

h/t Quartz