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Deodorant and Antiperspirant Testing


As embarrassing as it it to admit, sometimes my armpits stink with BO. I'm not talking about a sweaty, vinegary smell. I'm taking about full blown BO that smells like bad cumin and rotten onions. However, I have NEVER smelled BO on my husband (even after mowing the grass on a 90 degree day). My BO isn't strong enough to clear a room, but I can smell it. Most people who bathe daily and wear deodorant don't have significant BO problems. However, some people still struggle with BO even though they bathe daily and wear deodorant/antiperspirant because their bodies are just prone to it. I decided to test if deodorants/antiperspirants are actually reducing the amount of bacteria in the armpit. If you don't want to read this long page, click here for the short Spoiler Results Summary

    BO Basics

    • BO is caused by a combination of your body chemistry and your particular microbial flora. Genetics are involved and the ABCC11 gene has been implicated. About 2% of people don't stink at all while some unfortunate souls inherit really stinky armpits. 
    • Your body has 2 types of sweat glands. The eccrine sweat glands just release sweat and salt and are not blamed for BO. The apocrine sweat glands (which open into hair follicles and become abundant under the armpits during puberty) release proteins, fats, and other molecules. Some people secrete too much from their apocrine glands.   
    • Certain microbes in our skin break down the normally odorless molecules secreted from our apocrine glands and turn them into pungent thioalcohols (which smell similar to really bad onions or bad cumin). Some bacteria produce more stink than others. For example, some people's armpits are colonized with Staph Hominis which is known to produce a lot of stink. 
    • Your diet, medications, genetic conditions, and diseases such as diabetes can affect your BO. Being constipated is even thought to make BO worse.
    • BO is NOT removed from a shirt in the laundry that is washed on cold.  At least, I have yet to find a detergent that gets BO out of clothing in cold water. Smell the armpits when the shirt is warm in the dryer, and you will still smell the BO.
    • BO that was not removed in the washer, can reactivate and "reappear" when the shirt is worn again and your body warms it up. So, you might think YOU smell and that your new deodorant isn't working, but it is really old BO embedded in your shirt. 
    • Some deodorants/antiperspirants that work for me, might not work for you. Everyone is different. 
    • Some people don't have a good sense of smell and don't smell BO. I have a very good sense of smell. 

    How deodorants and antiperspirants work

    Antiperspirants contain aluminum salts which plug up your sweat gland pores to keep you from sweating. The thought is that if your armpits are dry, bacteria won't grow and won't produce the smell. Also, if they stop the apocrine glads from secreting the precursor molecules, the bacteria in your skin won't be able to produce the smell. Usually this works. However, there is a concern that aluminum is bad for your health. In addition, aluminum containing deodorant causes the armpits of your white shirts to turn yellow in as little as one wearing. 

    Deodorants do not contain aluminum and do not stop sweating. They work by attempting to decrease the number of bacteria in your armpits. Some deodorants make the armpit too salty or acidic for bacteria to grow. Some use essential oils or silver to inhibit bacterial growth. 

    Experiment Procedure

    I decided to test deodorants and antiperspirants to see which decreased bacterial growth in my armpits and which stopped BO the best. To do these experiments, I swabbed both of my armpits right after a shower to see how much bacteria was on them when I was clean. I always showered and washed my armpits using a washcloth and Dove unscented soap. (I never used antibacterial soap.) I shaved my armpits. 

    I rubbed those swabs onto agar plates. 

    Then I would put one deodorant/antiperspirant under one armpit and no deodorant at all under the other armpit. I would go about my day without showering again. After 24 hours, I would swab both armpits again and do a sniff test. (I have a great sense of smell.) I incubated all agar plates at 98 degrees F in my incubator for about 72 hours, and then took photos of the plates. I repeated these experiments with each deodorant on several different days to be sure of of my results. It is also important to note that the "clean armpit" plates had 24 extra hours to grow compared to the dirty armpit 24 hour plates. (So the "clean armpit" plates look like they have a similar amount of bacteria on them to the dirty armpit plates, when in reality, the clean armpits right after a shower had significantly less bacteria than the dirty armpits 24 hours after a shower.)

    About Agar Plates

    In case you are new to looking at agar plates, let me explain. The whitish/yellowish dots on the plates are colonies (or piles) of millions of bacteria. Not all types of bacteria can grow on these agar plates. Viruses can NOT grow on these agar plates. Yeast, mold, and fungus CAN also grow on these plates. In general, the more colonies that grow on the plate, the more germs there were on the surface that was swabbed. However, a clean agar plate does not necessarily mean that no germs whatsoever were present on the surface, because not everything can grow on an agar plate. 

    Lume Deodorant


    Lume is an all-natural deodorant that was invented by a female OBGYN as a way to help women who smell "down there". It is a lotion that can be used under your arms AND on your private parts. (You are not supposed to put it INSIDE your body. Just on external private parts.) It works by reducing the growth of the stink-causing bacteria. I have been using Lume for 1.5 years and love it. It does not block sweating. It just blocks the smell. It has not discolored or harmed any of my shirts. The directions are to rub a small pea-sized amount all over your clean, dry armpits. This is how much I use daily and for my experiments one one armpit. It does not have a wet or greasy feel. They have other scents, but I tested and use the Lavender Sage scent shown in this picture. 

    For these experiments, I swabbed both of my clean armpits after a shower. Then I put a pea-sized amount of Lume under one armpit and nothing under the other armpit. I went about my day (which always involves exercise and sweating) and swabbed my armpits again about 24 hours later. Some of the plates are labeled "new lume" because I got a second bottle of Lume partway through the experiments. Here are the results. 

    My results show that there was significantly less bacteria growing on the plates from the Lume armpit compared to the plates from my armpit with no deodorant at all. These results strongly suggest that Lume deodorant does inhibit bacterial growth. My "smell-test" also indicated that the Lume armpit never smelled, but the no deodorant armpit STUNK!!! Of course, I already knew that I wouldn't smell with Lume because I had been wearing it for a year already. (There also might be other mechanisms by which Lume fights BO in addition to reducing the growth of bacteria.) 

    I also tested Lume on my 15 year old son. He refused to let me swab his armpits, but we did a smell test. He put a pea sized amount of Lume under one armpit and no deodorant under the other on a day when he was staying home to do yard work. The test only went for 9 hours, but his no deodorant armpit stunk and the Lume armpit smelled fine after 9 hours. Lume also has some residual activity. It took 2-3 days after wearing Lume for my armpit to stink. (I would shower every day and not put on any deodorant, but the Lume armpit took 2-3 days to stink again.)

    If you would like to order Lume and try it for yourself, please click here to go to the Lume website. You should be able to tell if Lume works for you. If you don't have a good sense of smell, hopefully you have a close friend or family member who will be honest with you and let you know if you stink. It might take a few days of using Lume for your armpit pores to unclog and for Lume to start working for you. It worked for me immediately. You also have to be sure you aren't wearing BO infested clothing. Lume is available in stick form or a tube of lotion. The "stick" is just for people who can't wrap their heads around the concept of rubbing a lotion under their armpit. The stick is just plastic with the lotion coming out of the top. I recommend just buying the tube of lotion. Lume also has the most entertaining and informative commercial that you can watch at the bottom of their home page. After I got my experiment results showing that Lume was great, I signed up to be a Lume affiliate. So, if you order Lume through my link, I'll get a small commission. That is the money that I use to do my experiments. However, I would never recommend a product just to get a commission. I only recommend great products. 

    Tom's Wild Lavender Deodorant

    For these experiments, I tested Tom's Wild Lavender deodorant. It has a VERY STRONG lavender smell. It has a wetter/greasier feel when you are wearing it compared to the Lume or Secret. I swabbed both of my armpits after a shower and rubbed those swabs on agar plates. Then I put 8 passes of the Tom's deodorant under one armpit. I put nothing under the other armpit. I went about my day which always included exercise and sweating. I swabbed my armpits again after about 24 hours. 

    My results for Tom's are not as obvious as for Lume. There does seem to be a little less bacteria on the plates from the "Tom's deodorant" armpit than from the "no deodorant" armpit. So, Tom's may have some antibacterial activity. My sniff test revealed that I never had BO during the test, so the Tom's lavender deodorant did work for me. I still smelled like lavender after 24 hours. If you would like to order this Tom's Lavender Deodorant , you can order it here on Amazon


    Nuud is an all natural, vegan, aluminum-free deodorant from the Netherlands. It uses microsilver to supposedly kill germs and stop stink. It does not stop sweating. They say that one application works for 3-7 days even with showering and shaving every day. I found that hard to believe, but I decided to test it. After a shower, I swabbed each of my clean armpits and rubbed the swabs onto agar plates. Then I rubbed a small pea-sized amount of Nuud all around under one armpit. I did not put any deodorant under the other armpit. Then I went about my day which included exercising and sweating. After 24 hours, I swabbed my armpits again and did a sniff test. 


    As you can see, there is significantly less bacteria on the Nuud armpit plates compared to the no deodorant plates. This strongly suggests that Nuud inhibits the growth of bacteria in armpits. I also did not have BO in the armpit with the Nuud, but my other armpit STUNK! Nuud also had a significant residual effect. After I finished testing Nuud, I had to wait until I started to stink again before I could test another deodorant. It took a whole week of showering daily and wearing no deodorant at all for my right armpit (the one that had the Nuud on it) to get BO again. If you would like to order Nuud, it is available here on Amazon.


    Secret is an aluminum containing deodorant that plugs up pores to keep you dry. To test this antiperspirant/deodorant, I swabbed my clean armpits right after a shower and rubbed the swabs on agar plates. Then I put 8 passes with Secret under one armpit and no deodorant under the other. Then I went about my day which included exercise and sweating. After 24 hours, I swabbed both arm pits and did a sniff test. Here are the results.

    The results show that there is dramatically less bacteria on the plate from the Secret armpit compared to the no deodorant armpit. These results suggest that Secret is very effective at reducing the amount of bacteria in the armpit. My armpit with Secret did not smell bad. My "no deodorant" control armpit smelled terrible, of course. Secret also lasts a few days. You can see that the "clean left armpit" on 9/15/2019 did not have much bacteria on it. That is most likely because I had Secret on that armpit the day before, and it was still working. Even with showering every day, it took a few days for the Secret to wear off and for me to get BO again. (I showered every day but didn't put any deodorant on, and it took a about 3 days after using Secret for me to get BO again.)

    Conclusion and Future work

    My results strongly suggest that some natural deodorants like Lume and Nuud keep BO away by reducing the amount of bacteria growing in the armpit. They may have other mechanisms by which they also get rid of BO that I did not investigate. Secret deodorant/antiperspirant also seems to significantly reduce the amount of bacteria in the armpit. If there is another deodorant or antiperspirant that you would like me to test, please contact me and let me know. 

                                                Thank you!--Annie Pryor, Ph.D.