Do you smell bad? Just throw on some bacteria

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!

Treating severe nickel allergies with probiotics

Buffalo nickel, made of 25% nickel.

Systematic nickel allergy syndrome (SNAS) is a severe reaction to nickel, a metal that is found in nature and most human food sources. An allergic reaction to nickel can manifest cutaneously, causing inflammation and irritation of the skin, or it can be gastrointestinal, causing diarrhea. Studies in which balanced diets are used as a way of reintroducing nickel to SNAS patients have been conducted to find possible treatments of this allergy; however no cure has been found. Research by a group in Italy was published last month in the Journal of Applied Microbiology that examined the use of probiotics such as Lactobacillus reuteri to treat SNAS patients.

A double blind study was performed using twenty-two adult women who had both systematic and cutaneous reactions to nickel. A control group received a placebo, while an experimental group received the L. reuteri probiotic. Fecal sampling and clinical evaluations were performed at the start of the study, before any pills were taken, as well as after two weeks of supplementation and two weeks after the end of the trial. Throughout the entire evaluation period the patients followed a low-nickel diet.

Both groups prior to experimentation had low diversity of lactic acid bacteria (LAB) communities in their gut.  After the trial, they found that the control group had stable LAB communities while the experimental group resulted in greater diversity of LAB than prior to the study. They found that only the experimental group showed the presence of L. reuteri meaning that the bacteria in the probiotic had successfully colonized and survived in the gut, an essential feature if a probiotic is to be used in a clinical setting.

They also found a significant improvement in cutaneous symptoms after two weeks in both the group being given the probiotic with a low-nickel diet, as well as the strictly low-nickel diet patient group, however the improvement was more pronounced in the group getting the probiotic. Only patients receiving the supplementary L. reuteri showed a significant reduction in gastrointestinal symptoms. Eating a diet low in nickel will cause less averse reactions than an uncontrolled diet; however, this study strongly suggests that probiotics can significantly decrease the severity of allergy symptoms in SNAS patients. The study also suggests that a combination of diet and probiotics could increase bacteria’s ability to colonize in the intestines. Further long-term studies on the prolonged effects of probiotic use in treating SNAS and other conditions will allow us to better understand how to use probiotics to manipulate the microbiome and treat disease.