Experiments Home‎ > ‎

Deodorant and Anti-Perspirant Testing

As you have probably noticed, some people have terrible body odor and others don't. As embarrassing as it it to admit, sometimes my armpits stink with full blown BO. However, I have NEVER smelled BO on my husband, even after mowing the grass on a 90 degree day. My BO isn't bad enough to clear a room, but I can smell it. It is personal BO deep in my armpits. 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. 

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 usually 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, 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 unless it is washed on warm or hot. Cold water does not remove BO. I have done many experiments to prove this. (At least, I have yet to find a detergent that gets BO out of clothing on cold). 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, will 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 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 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. I used aluminum containing Secret deodorant for many years. Many days, I would step out of the shower and STILL have a BO smell in my armpits. I don't know why. It was like it trapped the BO in my armpit. That never happens anymore now that I don't use an antiperspirant. 

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. 

Which deodorant kills germs and gets rid of BO the best?

I decided to test deodorants and antiperspirants to see which decreased bacterial grown in my arm pits and which reduced BO the best. To do these experiments, I would swab both my armpits right after a shower to see how much bacteria was on them when I was clean. 

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 and swab my armpits again and do a sniff test after 24 hours. The agar plates were incubated in my 37 degree F incubator for about 72 hours and then I took photos of the plates. I repeated these experiments with each deodorant on several different days to be sure of of my results. 

Lume Deodorant