FEB 06, 2016 3:31 PM PST

Antiperspirant and the Armpit Microbiome

WRITTEN BY: Kerry Evans
Antiperspirant and deodorant keep you smelling fresh, but they also alter your armpit microbiome.

The microbiome continues to be a hot topic.  Sometimes it’s also a stinky topic, like when it has to do with armpits.  Researchers at North Carolina State University just published a study on the armpit microbiome. According to author Julie Horvath, “we wanted to understand what effect antiperspirant and deodorant have on the microbial life that lives on our bodies, and how our daily habits influence the life that lives on us”.
 
Antiperspirants increase bacterial diversity.


First off, there’s a difference between antiperspirant and deodorant (this was news to me). Antiperspirants contain aluminum salts that block sweat production.  Bacteria find lots of tasty nutrients in your sweat, so less sweat means fewer bacteria.  Deodorants simply use antimicrobials to kill bacteria.

For the study, Horvath and colleagues swabbed the armpits of 17 participants for 8 days.  On the first day, the participants followed their usual routine - some used deodorant, some used antiperspirant, and some used nothing at all.  On days 2-6, the participants did not use antiperspirant or deodorant.  Then on days 7-8, all the participants used antiperspirant.

As expected, there were more bacteria, around 750 CFU, in their armpits when no deodorant or antiperspirant was used.  When the participants all used antiperspirant, the numbers decreased to around 73 CFU.

However, the researchers were surprised to find that antiperspirant actually increased bacterial diversity. Participants who did not regularly use antiperspirant or deodorant had the most Corynebacterium (these species are responsible for “body odor”).  For participants who regularly used deodorant, 61% of their armpit bacteria were Staphylococcus, 29% were Corynebacterium, 5% Anaerococcus, and 5% were other species.  For antiperspirant users, however, 60% were Staphylococcus, 14% Corynebacterium, 4% Anaerococcus, and a whopping 22% were other species.

It’s not clear whether these changes are good or bad for your overall health.  According to Horvath, Within the last century, use of underarm products has become routine for the vast majority of Americans … yet, whether use of these products favors certain bacterial species – be they pathogenic or perhaps even beneficial – seems not to have been considered, and remains an intriguing area needing further study”.


Sources: North Carolina State University, Wikipedia

 
About the Author
  • Kerry received a doctorate in microbiology from the University of Arkansas for Medical Sciences.
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