Do probiotic deodorants really work?

Summer is finally here. That means lots of sunshine, beaches, hiking, and (for me, at least) armpit stains.

I’m tired of ruining my white shirts with nasty yellow-brown sweat blotches. So this spring, I decided to look into alternatives. Believe it or not, it isn’t your sweat that causes those noxious stains—it’s the aluminum salts in your antiperspirant. That’s why I was intrigued by the new wave of probiotic deodorants; underarm salves that supposedly use a healthy mix of bacteria to combat body odor without the chemicals that cause armpit stains. So myself and five other Popular Science staffers put these products to the test. This is what we found.

But first, we need to talk about your B.O.

Why do my armpits smell?

What you eat can influence your body odor. Eating a lot of meat, for example, might make your armpits stinkier.

Genetics also seem to play a role. People of East Asian origins have a lower chance of having body odor, because their underarm glands don’t secrete much. (Jealous? Me? Definitely not…)

But the main thing is your bacteria. Sweat by itself doesn’t actually smell. It contains long chains of molecules that are too heavy to vaporize and reach your nostrils. But the bacteria in your pits break down these big molecules into smaller molecules that fly off, and depending on what kind of bacteria are living on you, those volatiles can smell pretty foul.

In particular, scientists point to Staphylococcus hominis, Corynebacterium tuberculostearicum, and bacteria in the Anaerococcus family as some of the culprits of B.O. Meanwhile, there’s some evidence that Staphylococcus epidermidis and Propionibacterium acnes might be sweeter smelling. But researchers are still trying to tease out all of these are relationships.

How does deodorant work?

Deodorants work by killing off the bacteria in your armpit and adding a perfume. A lot of commercial deodorants also contain antiperspirants that plug your sweat ducts, so that less perspiration comes within reach of those smell-producing bacteria in the first place.

But while your Speed Stick is indiscriminately killing off microbes in your armpits, it might also be opening up new territory for bacterial colonists.

“If you use underarm cosmetics, you will kill a lot of bacteria,” says Chris Callewaert, a postdoctoral researcher studying armpit microbiomes at UC-San Diego. “You’ll have fewer bacteria, but the diversity goes up enormously, so you’ll have all different kinds of bacteria that normally wouldn’t be there if you don’t wear antiperspirant. That’s not necessarily bad, but you are screwing up your underarm microbiome. And we see in smelly armpits, the diversity is also very high.”

In a study of more than 300 underarm communities, Callewaert found hints that deodorant could actually make B.O. worse in some cases. He found that people who used antiperspirants had higher concentrations of malodorous Staphylococcus bacteria.

Callewaert has also, in a few instances, managed to transplant bacteria from non-smelly armpits to eradicate bad bacteria in stinky armpits. It worked in a study with two twins, and on Callewaert himself, he says, thanks to an old bacteria-smeared t-shirt he had lying around.

For these reasons, it’s plausible that a probiotic deodorant could help treat body odor, by encouraging good bacteria to grow.

Should I be worried about the chemicals in my deodorant?

This was something that kept coming up when I told people I was testing a probiotic deodorant—several friends said they wanted to switch to something else because the chemicals in deodorant are supposed to be “really bad for you.” But looking into it, I found out there’s really no evidence that antiperspirants increase your risk of developing cancer. Several studies have looked into it and found no link. A 2008 review of all the research on this topic found “no scientific evidence to support the hypothesis.” The National Cancer Institute (NCI), American Cancer Society, Susan G. Komen Cancer Foundation, and BreastCancer.org all agree that your deodorant appears to be safe. Nevertheless, it’s an area of ongoing research.

What we found

We tested six probiotic deodorants that we found on Amazon and Etsy. For two weeks, each Popular Science staffer wore his or her regular deodorant on one armpit, and tested the probiotic on the other, to make the experiment as controlled as possible. Every day, we rated how much each armpit was sweating and how bad it smelled.

Handcrafted Honeybee, $12 for 2.65oz

I tested this one personally, and my trial got off to a bumpy start—literally. I got a rash on the first day. But that’s a pretty common reaction to deodorants that contain baking soda, which helps to neutralize some of the acids in your sweat. I took a break for a day to let it heal, and when I tried it again it worked out ok.

The texture is crumbly, which is kind of annoying, and not just because of the mess. Watching little bits of such an expensive deodorant fall onto the floor felt like watching money burn.

Within the first few days of trying this deodorant, my pits got super swampy. I’m not sure I’ve ever produced so much sweat while just sitting around, and this was in early springtime, so I couldn’t blame the weather. This is apparently a normal thing that happens when you’re weaning yourself off an antiperspirant. Eventually my sweat levels stabilized, and now that I’ve been wearing this deodorant for a few months, I feel like I’m sweating the same amount as I did before I started the trial.

I was definitely a little stinkier at first. One night, after a very long day, I had to skip a shower. The next morning I smelled worse than I ever have in my life—in both armpits, but particularly my probiotic one. And at first, I had to re-apply the deodorant right before exercising or I’d get super smelly. But these days I generally get along just fine with a single application, and I don’t smell anything. In fact, I think it worked slightly better than an aluminum-free, non-probiotic deodorant that I also sampled.

Interestingly, I suspect (/hope) that I may be cultivating less smelly microflora in my armpit. I’ve noticed that I can now go for longer periods of time without wearing any deodorant, and I don’t get so smelly when I work out. It’s not as good as when I was wearing the antiperspirant, but the difference is not really noticeable.

The stains on my shirts also seem to be going away. There might be slight yellowing, but I think it washes out pretty easily.

Overall Rating: 7/10

Organic Island, $13 for 2.5oz

Staff Writer Kendra Pierre-Louis did not like this deodorant. Although she didn’t mind the smell or the texture, and it didn’t effect her clothing, the puddles of sweat were a showstopper. “It left me moist to a degree that I found unsettling,” says Kendra. The swampy pits set in around the second day and continued until she gave up wearing it, about a week in. “I was wetter with it than I am when I don’t wear any deodorant,” says Kendra. “I’d rather not use anything, and maybe smell a bit more.”

Overall rating: 3/10.

Dirty Stash Bath Co., $10 for 2oz

Assistant Editor Claire Maldarelli tried this one, and for the first few days she really liked it. “My armpits get irritated from my regular antiperspirant. This wasn’t as drying—it was more moisturizing.” And unlike her usual deodorant, this one didn’t cake up on her shirts. But the consistency was a little off. “I would have to put it on it over the sink so that stuff wouldn’t just fall everywhere,” she says.

But by the end of the third day, Claire says she started sweating a ton. She didn’t feel like she smelled, but the sheer amount of sweat was uncomfortable.

“What stopped me from keeping going with it was the fact that it didn’t help the amount of sweating,” she says. “But if you’re someone who doesn’t sweat a lot, I feel like it would be fine.”

Overall rating: 6.5/10

Return to the Roots Herbal Deodorant, $9 for 3oz

Senior Editor Sophie Bushwick was relieved to go back to her regular deodorant after trying this one. “The texture was tacky and unpleasant, and it crumbles when you put it on,” she says. “I had to hold it in my armpit for a while so it could warm up and go on smoothly.”

Her probiotic armpit was consistently smellier and swampier than the one sporting her usual deodorant, and there were equal amounts of staining/caking on both pits. She said she thinks this worked better at masking foul scents than a Tom’s of Maine product she’d tried a few years earlier, however.

Overall rating: 4/10

Hygge Body, $13.50 for 3.75oz

“I was a sweaty mess by the end of the second day,” says Social Media Editor Mallory Johns. “I frantically over-perfumed to cover my right armpit smelling like a swamp.”

This deodorant was hard to apply evenly—it came on in streaks. And Mallory consistently rated her probiotic armpit as smellier and wetter.

On Day 8, “I was at a concert dancing around for two hours straight, and by the time I came home, my husband said I smelled so funky he didn’t want to go anywhere near my arms.” Then she got a rash on Day 10 and (gladly) concluded her experiment there.

Overall rating: 4/10

6. Dirty Hippie, $19 for 2.5oz

Senior Producer Tom McNamara normally wears an organic deodorant, so he didn’t really notice a difference in sweat levels or smell with this probiotic deodorant. “I don’t think it improved my body scent overall,” he says, “but I don’t think it was too bad to begin with.”

Tom liked the smell of this deodorant, and the cardboard Push Pop-style tube that it comes in felt more Earth-friendly. But during a heat wave, the deodorant melted into the cardboard and wouldn’t slide up anymore. “So I had to scoop it with my fingers,” says Tom, “which actually I found to be a better application method in general. It’s like putting on lotion, but more clay-like.”

There was a bit more caking on his shirts, but the biggest difference was in price—Dirty Hippie costs twice as much as Tom’s regular deodorant, with about the same level of effectiveness. “I don’t feel like there’s some magic new bacteria on my body fighting, like, Darth Vader bacteria,” he says. “But overall, yeah, I’m cool with it.”

If it weren’t for the price (and the fact that it takes forever to ship from New Zealand), Tom would have given this a score of 8 out of 10.

Overall rating: 5/10

So … do probiotic deodorants work or not?

The answer to this question depends on what’s important to you. If regular products aren’t working, and you’re ok with sweating quite a bit more and spending the extra dollars, a probiotic deodorant might be worth trying. The textures were almost universally unpleasant, and chances are you won’t smell quite as good, but the probiotic deodorants did tend to reduce effects on our clothing.

If you still feel paranoid about the chemicals in your off-the-shelf variety, or you just feel like trying something greener, I’d recommend starting with a (non-probiotic) “natural” deodorant that you can buy in most supermarkets. It’ll be a cheaper way to test whether you have the stamina to sweat profusely for several weeks until things level out again. (And it does take several weeks for the effects of the antiperspirant to wear off, says Callewaert, so you’ll have to be patient.) If that goes well but you still feel kind of smelly, then it might be worth shelling out extra for the probiotic deodorant. Maybe.

But do your research. Several of the “probiotic” deodorants I saw on Etsy didn’t seem to contain any actual bacteria, and some claim they kill bacteria, which is literally the opposite of what a probiotic is supposed to do.

The types of bacteria matter, too. Most of the probiotic products available today contain Lactobacillus acidophilus, which is ordinarily a gut bacteria. “These microorganisms don’t naturally occur on the skin or in the armpits, so the effect will be minimal or very temporary,” says Callewaert.

A better strategy would be for companies to mix in Staphylococcus epidermidis and Propionibacterium acnes—those naturally occurring armpit microbes that may be correlated a better smell. But at this point it’s just a lot easier for companies to get their hands on L. acidophilus, since it’s mass-produced as an intestinal probiotic.

We’re still in the early days of understanding the underarm microbiome and its effect on your body odor. Hopefully, as scientists learn more about what’s going on in our armpits, they’ll be able to design more effective probiotic deodorants. Till then, good luck out there, and try not to sweat the small stuff.