When you’re next to someone on the subway or on the street who smells bad, do you ever wonder what it is on his or her body that is making him or her smell that way? I don’t. I usually just walk away and I’m done with it. But after reading a new study out of Switzerland and published in Microbiome, the next time I’m standing next to a smelly person on the subway, I might ask him or her about the bacterial makeup of his or her armpit. While body odor has long been attributed to the degradation of bodily fluids by bacteria in armpit sweat glands, this new study sought to identify which bacteria cause body odor.
The study consisted of 24 test subjects, both male and female, of which 13 used an antiperspirant and 11 did not, as well as four trained assessors tasked with smelling and analyzing the test subjects' underarms (talk about a fun job). Unsurprisingly, the researchers found that sweat odor intensity was much higher in non-antiperspirant users. In addition, the non-antiperspirant users' odors were more likely to be described as sulfury-cat urine, acid-spicy, and fresh onion as compared to those that used antiperspirant. After analyzing the amount of bacteria in the armpit of all the individuals, they found that those not using an antiperspirant had 50 times more bacteria than those using one.
The researchers were able to associate specific groups of bacteria with body odor: Corynebacterium, for example, had higher abundances in the smelly pits, while Propionibacterium had higher abundances in the non-smelly pits. Overall, bacteria from the Firmicutes and Actinobacteria phyla were the most prevalent in all the arm pits, which makes sense as they are typically the most prevalent bacteria on the skin. Finally, some bacteria were found to be more prevalent in men than in women, evidence that lends itself to the belief that men and women have different odors.
The identification of the smelly arm-pit bacteria provides an opportunity for microbiome interventions to combat body odor, and several companies, like AOBiome, are currently trying to do this. They have developed products that are meant to put bacteria on the body that will help control body odors. There are people out there (some that I know!) that rarely if ever take showers or use antiperspirants…and they actually smell just fine. Talk about dedication to the microbiome!