Can a Daily Bacteria Spray Really Make You Smell Better Without Soap?

Courtesy Mother Dirt
Courtesy Mother Dirt / Courtesy Mother Dirt

Years ago, as an exchange student living in Russia during a particularly swampy summer, I decided to forgo showering every day, mostly to avoid hogging my host family’s single bathroom or, worse, having to discuss the etiquette of turn-taking in my broken Russian. I started to notice that I got sweaty, but I seemed to smell the same regardless. Ever since, I’ve stretched my showers out longer and longer, depending on the season: from once a day to once every two days to (sometimes) once every three days, if I’m busy or particularly forgetful that week.

Last fall, I made a bigger change in my hygiene routine, one I was less confident in: I threw away my “clinical strength” Secret antiperspirant. In the process, I also cleaned out my shower, chucking my soap, my shampoo, and my conditioner, my deep-conditioning hair masks, and my mousse. I replaced my favorite toiletries with a small spray bottle filled with a cocktail of bacteria designed to approximate the experience of rolling in a pile of dirt every day, but, you know, minus the actual dirt—and yet improve my skin and odor.

The Massachusetts-based personal hygiene company Mother Dirt was founded on the idea that clean shouldn’t necessarily mean sterile. Its flagship product, the AO+ Mist, was invented by a chemical engineer who hasn’t showered in 12 years. While the company doesn’t sell the mist as a substitute for showering or lathering up, it contends that by spritzing a type of dirt-borne microbe called ammonia-oxidizing bacteria on your body twice a day, you can have softer, better-smelling skin, naturally. The AO+ Mist, Mother Dirt says, is “formulated to restore balance to skin microbiome, resulting in the improved appearance and resilience of the skin.” In other words, if everything goes right, you might not even want soap or lotion—your skin will be just fine on its own, thanks to the bacteria eating up that smelly ammonia.

Drawn by promises of spending even less time on my morning routine than usual, I was sold. Mother Dirt sent over samples of its full hygiene line—the AO+ Mist as well as microbiome-compatible shampoo and cleanser—and I promised myself I would not let any preservative-laden beauty products touch my skin for a month. Preservatives, a Mother Dirt spokesperson assured me, would decimate my skin’s “good” bacteria, and I wanted my bacterial colonies as robust as possible. These odor-fighting microbes are delicate creatures, and the company’s studies have shown that they’re relatively easy to kill, be it with shampoo or just a month spent at room temperature. Even refrigerated, the ammonia-oxidizing bacteria in the spray can only survive six months.

Before the company sent me a sample of the AO+ Mist, they made me assure them that I read the following disclaimer, which is careful to avoid making any concrete claims about the product’s efficacy:

The products help users maintain a balanced microbiome on their skin. The net effect of this is an improvement in the look and feel of their skin.This includes anything from improvements in hydration, the balancing of oil production, (helping with both oily and dry skin), improvements in body odor and the overall soothing of the skin. Because of these benefits, users find that they can cut down or cut out cosmetic products like soaps, deodorants, moisturizers etc.

According to the creed of Mother Dirt and its parent company, AOBiome LLC, it’s the bacteria in dirt that, ironically, used to make us cleaner and better in Ye Olde Days before indoor plumbing. While outside researchers caution that there’s still a lot of work to be done to understand the skin’s bacterial makeup, it’s not a crazy idea.

Ammonia-oxidizing bacteria like the ones in AO+ Mist do exist in soil. Scientists have been able to isolate these bacteria, which convert ammonia into a useable form of nitrogen for plants, since the late 1800s. Nitrosomonas, the genus AOBiome uses, exists in natural bodies of water as well as dirt. And so it's not far-fetched to think that when more people had daily, constant contact with soil, these bacteria would be more plentiful on the skin. Body odor occurs because the bacteria living on our skin break down molecules of sweat into smelly compounds, and in theory, changing the makeup of your skin bacteria could change those smells.

Ammonia-oxidizing bacteria are the “nitrofiers” in the bottom right of this diagram on Earth’s nitrogen cycle. Image Credit: Eme Chicano via Wikimedia Commons // CC0 1.0

In order to really see the difference between my life before and after the AO+ Mist, I decided to do everything I could to cultivate a welcoming skin habitat for the bacteria spray, including forgoing regular soap and shampoo as much as possible. During my first few days using the mist, I amended my personal hygiene routine to suit the whims of the bacteria.

Every morning, I washed my face with Mother Dirt’s preservative-free, all-purpose cleanser, rather than a traditional face wash. About once a week, I used the Mother Dirt shampoo, occasionally supplementing my hair routine with “no poo” alternatives like diluted baking soda and vinegar rinses, free of the preservatives I was anxious to protect my ammonia-oxidizing bacteria from. When I emerged from the shower, I rubbed some “natural” branded deodorant on, then sprayed the AO+ Mist on my armpits, scalp, and crotch. When I was feeling industrious, I spritzed my feet and other parts of my body I thought could use an extra dose of smell-sucking bacteria. At night, I repeated the spray ritual.


There is some research to back up the idea that modern living has changed our skin microbiome. Chimpanzees, humanity’s closest living relatives, have more diverse bacterial communities on their skin than humans do, according to a recent study [PDF]. Other primates show much higher concentrations of soil-related bacteria and a much lower concentration of Staphylococcaceae, the bacteria family that includes the germs underlying staph infections.

There’s not enough research to say for sure when the human skin microbiome split off from our primate relatives, but there’s some evidence that our living habits might have played a role. A study of isolated hunter-gatherers in the Amazon found an incredible diversity of skin and gut bacteria, showing a 40 percent increase in microbial diversity compared to the modern industrialized populations. U.S. populations had much higher concentrations of bacteria species like Staphylococcus compared to these hunter-gatherers.


Not to mention that recent research indicates that wearing antiperspirant changes your skin microbiome in substantial ways, altering both the composition and number of bacterial colonies in our armpits. A 2014 study suggested that this change of the armpit microbiome actually made people smell worse, though it only analyzed nine volunteers. Dandruff, too, has been linked to the balance of skin bacteria on the scalp.

“You’re wiping out your body's ecosystem, and whatever can grow back, now there’s no other microbe competing for resources,” Julie Horvath, head of the Genomics and Microbiology Research lab at the North Carolina Museum of Natural Sciences and a research associate professor at North Carolina Central University, tells mental_floss of antiperspirant use.

In a 2016 study of the differences in the armpit bacteria of people who wear deodorant and antiperspirant and those who don’t, Horvath and her colleagues found that when habitual antiperspirant users stopped applying the stuff, the bacteria that grew back in their armpits were different from the species that typically make up the microbiomes of people who don’t use products. The armpit bacteria of people who suddenly went au naturel became inundated with bacteria from the Staphylococcaceae family, while non-users’ pits were full of Corynebacterium bacteria [PDF]. Both these types of bacteria produce odors, and it’s still unclear what these different population densities might mean for our health. But it’s clear that deodorant and antiperspirant have a measurable effect on our microbiome.


My new bathroom routine was certainly a lot more work than the old one, even if it included fewer products. Because I wanted to keep the spray fresh for as long as possible, I kept it in my refrigerator—not a terribly intuitive place for a personal care product. I often forgot about it completely, skipping one of my spray sessions for the day, or wound up standing in my bra in the kitchen I shared with three roommates, sneakily applying bacteria to my armpits and spraying the mist down my pants in front of the fridge, hoping no one would walk in on me. When I packed my bag with essentials for staying at the apartment of my boyfriend at the time, a 45-minute commute across Brooklyn from my own, I left it at home. As much as I wanted to stick to the twice-daily routine, taking it would mean leaving the bottle on my desk at work all day, where my precious bacteria would surely die a hot death.

Courtesy Mother Dirt

Over the course of my experiment, I actually began showering more, hoping to cut down on the smells that the mist and weak natural deodorants didn’t subdue. After a month, my preservative-free, bacteria-friendly shampoo and soap from Mother Dirt expired, and I didn’t replace it, opting to test out a completely soap-free lifestyle for a while. I was bathing more often, though I probably still managed to save some water compared to my usual routine. When you aren’t using soap or shampoo, there aren't a lot of ways to keep yourself occupied in the shower. Deprived of my usual wash routines, I didn’t really know what to do with myself in there. My 10–15 minute showers turned into 5-minute rinses that still felt long. I often found myself yearning for a reason to kill time in the warm water, since the number of products I typically applied to my body had dwindled to, for most showers, zero. I was at a loss as to how I was supposed to shave without a lubricant like soap, but I managed to mostly not injure myself while taking dry swipes at my armpits with a disposable razor (shaving made me smell better, I rationalized).

Without extra-strength deodorant, I could no longer go days without a shower, and I became obsessed with my smell. Before the experiment, I had never paid particular attention to ridding my skin of bacteria, except when washing my hands, and I was surprised by how resilient the stench-producing colonies in my bodily crevasses were to my efforts to scrub them away with plain water. I missed being able to emerge from the shower with a seemingly blank slate of a body, devoid of embarrassing odors. I kept thinking of those deodorant advertisements where women inevitably scare away potential suitors by exposing a sweaty, smelly underarm. Was I that woman?

Perhaps in some circles, I was. Hygiene standards are cultural and have changed radically over time as things like indoor plumbing and hot water have become more widely available. In the U.S., showering every day, now taken for granted by many people, only really caught on in the 20th century, as late as the 1940s. By the mid-century, the public health movement of good hygiene as a way to prevent contagion had transformed into personal cleanliness as a social necessity. Schools screened films that told kids that if they didn’t adhere to stringent hygiene standards, people would dislike them, and they would never get dates. And then corporations reinforced those newly developed insecurities.

Since their very inception, deodorant ads have been designed to sow seeds of insecurity, particularly among women, who at one point in history thought perfume was enough to mask any icky bodily odors, much to the chagrin of the personal hygiene industry. One 1919 antiperspirant ad assured ladies that “even though there is no active perspiration—no apparent moisture—there may be under the arms an odor unnoticed by ourselves, but distinctly noticeable to others.” You think you don't need our product, these ads say, but you’re just oblivious to your own stench! These days, since most people already wear deodorant, Dove has resorted to telling women their underarms are not smooth enough (and in some cases, not white enough). Better go get some moisturizing, lightening deodorant, ASAP.

Furthermore, Americans’ obsession with cleanliness affects more than just our own skin. The products we use in the shower end up spiraling down our drains and into sewers. Wastewater typically spends some time at a treatment plant before it ends up back in rivers and oceans, but the water treatment process doesn’t catch everything. For several years, scientists have warned that traces of personal care products could be ending up in aquatic environments, potentially harming wildlife as well as human health.

Late last year, the U.S. passed a law banning the plastic microbeads commonly used in exfoliating soaps and body washes due to the high volume of the non-biodegradable beads ending up in waterways (enough to cover 300 tennis courts per day, one study estimated [PDF]). In 2004, Stanford researchers found that synthetic fragrances used in soaps, shampoos, deodorants, and other personal care products could be harming aquatic wildlife like mussels. In 2010, environmental scientists warned that certain ingredients found in shampoos and other household cleaning products could end up forming a carcinogenic contaminant in water supplies when exposed to chlorine in the water treatment process.

Research from the U.K. in 2009 indicated that the same bacteria-killing ingredient, called quaternary ammonium compounds, could lead to antibiotic resistance because of their presence in high concentrations in sewage. The FDA just banned most of the active ingredients in antibacterial soaps and body washes, on the grounds that their manufacturers couldn't prove that they were any more effective than plain soap, much less safe for long-term use.


By the end of my three months with the AO+ Mist, I didn’t become any less anxious about my potentially overwhelming personal odors than I had been during the first few days after quitting antiperspirant. In service to both my reporter’s notebook and my paranoid curiosity, I continued to stop to smell my armpits several times a day, often in the bathroom but occasionally at my desk at work. In my pre-bacteria days, I didn’t typically worry about other people noticing my smell—plus I was terrified of the smell that might greet me should I decide to poke my nose in my armpit—and consequently I have no idea if I smell any better or worse now than I did then. Certainly if I use natural deodorant, my body has a sweeter, less acidic smell than my clinical-strength antiperspirant pits, but I don’t know if that’s necessarily a good thing.

As my initial trial of the AO+ Mist wore on, it was hard to tell if the spray was working at all, though Julie Horvath, the deodorant-studying microbiology researcher, assured me that the AO+ Mist hypothesis seemed “grounded in science” and in line with other skin microbiome research. In my completely unscientific anecdotal experience, I didn’t seem to smell much better. I couldn't tell if the mist was offsetting any of the consequences of abandoning my high-strength antiperspirant.

In my quest for a less abrasive deodorant that wouldn’t wipe out my pit microbiome completely, I became well-acquainted with my body odor in a way I had not been while regularly slathering my pits with a solution of 20 percent aluminum zirconium tetrachlorohydrex gly (the active ingredient in many antiperspirants). I cycled through a variety of no-aluminum deodorants, from Arm & Hammer’s “Essentials” line of baking soda and plant extract gels (completely ineffective) to an unscented “24-hour protection” product from Tom’s of Maine (I smelled worse, like body odor and vinegar) to Funk Butter, a baking soda–based deodorant with the texture of dry wasabi that I had to apply carefully with my fingers. I spent $12 on a homemade deodorant that came in the shape of a bar of soap, but it only added a slight rosemary scent to the smell of my sweat. Finally, I plunked down $14 plus shipping for Soapwalla’s organic, vegan deodorant cream, and while I didn’t smell quite fresh at the end of the day, it at least kept me from worrying that people would start avoiding me over my pit fumes.


Where the change in my hygiene routine became most apparent, however, was not under my arms. The instructions for the AO+ Mist specifically suggested spraying the bacteria solution on your crotch—well-known as one of the body’s smellier areas. Like your armpits, your genital region is home to apocrine glands, the kind that produce smelly, pheromone-rich sweat in response to anxiety and arousal. But I was a little hesitant to go wild spraying bacteria into my lady parts. Messing with the vagina’s delicately balanced microbiome is an easy way to get an infection. So I limited my zeal for seeding new bacterial colonies to my pubes—hairs which, some scientists hypothesize, might be specifically designed to amplify odiferous pheromones.

Every time I pulled down my pants, a fetid breeze of moistly personal air wafted upward—a sensory assault of vaginal odor. My then-boyfriend, under pointed questioning, described the smell as being somewhat “fermented” and likened the effect to applying a magnifying glass to my previously more subtle feminine odors. I’m all for embracing my body’s natural tendencies, but going from having a relatively unremarkable eau de crotch to constantly smelling like my body had taken the worst kind of tropical vacation alarmed me. No matter how much I showered and sprayed, without soap, the pungent smell lingered.

The mist did have its highlights, of course. It absolutely made my skin feel softer and more hydrated. Not a drop of lotion touched my skin over my three-month course of twice-daily spritzing, which further satisfied my wallet and my environmental guilt over constantly buying new plastic bottles of chemicals to wash down the drain. While using the mist, my face looked smoother and clearer than ever before, even when I abandoned face wash for plain water. And though I didn’t smell great on a regular basis, the mist appeared to cut down on particularly excessive odors. If I gave my armpits a quick misting before I went to the gym, I felt like fewer noxious fumes emerged over the course of my workout.

But I did learn that lathering up, at least in the smelliest crevices of the body, is indeed vital to my hygiene routine. Much as I had hoped that my ammonia-oxidizing bacteria would come out in full force and dampen my natural smells enough to give up soap (which kills the bacteria, anyway), I eventually had to admit that I did smell more strongly than before, and not in a way I liked.


But the AO+ Mist, or something like it, may be more than just a complicated form of deodorant one day. The type of bacteria that that AOBiome is researching may have broader applications beyond cosmetics, though the company isn’t making any medical claims (which are much more tightly regulated than cosmetic ones) about its spray yet. A small preliminary study of 24 volunteers from the AOBiome team, presented to the American Society for Microbiology in summer 2014, suggested that ammonia-oxidizing bacteria might be beneficial for people suffering from acne. A Phase II clinical trial testing the spray’s safety and efficacy as an acne treatment wrapped up in March, indicating that the company may be moving toward FDA approval.

“Initially I was very skeptical, but after reading [the data] myself, I think that it’s quite plausible,” says Elena Barengolts, an endocrinologist and professor at the University of Illinois College of Medicine in Chicago who researches diabetes and the microbiome. She tells mental_floss that after reading through some of the research AOBiome has presented at conferences, she thinks the products may have therapeutic potential.

Using acne as the first model for inflammatory skin diseases, AOBiome is planning to explore other issues like eczema, rosacea, and diabetic ulcers, according to the company’s website. This is the type of application Barengolts sees the most possibility in. There’s the potential that this type of bacteria spray “could improve wound healing,” she hypothesizes, which would be particularly useful for diabetics, many of whom develop infection-prone foot sores.

However, as Horvath noted, there’s still a lot we don’t know about the skin’s microbiome. And not all people carry the same bacteria. The skin’s microbiome varies based on age, lifestyle, and even race. With small trials of only 20 or 30 people, it’s hard to say anything definitively about the AOBiome formula, other than that it’s not going to hurt you. Whether it’s worth throwing out your shelves full of personal care products in favor of a $50 spray bottle is the question.

For what it’s worth, I’ve started soaping up again, mostly—without the extra bacteria. I have ditched my face wash in favor of water and a little jojoba oil to combat breakouts, but I have returned my soap to its venerated place in the shower. I’m still using natural deodorant made with ingredients like clay and lavender oil, but I’m not sure it’s making any real difference in my pit microbiome. And while no one else has noted it to me, sometimes I smell weird.

If I had an extra $50 a month to spend on bacterial mist, I would totally incorporate it into my daily routine. With my current paycheck, though, it falls just short of being the life-changing product that would make such an expense worthwhile. Still, six months on, I still miss how soft it made my skin.