The Genetic Reason You Have B.O.

May 19th 2016

Lucy Tiven

If your armpits stink, your genes may be to blame.

According to a 2013 study published in the Journal of Investigative Dermatology and reported by Live Science, a single gene variant determines whether or not your underarms emit body odor.

Will you "pee-ew"?

The study looked at 6,495 British mothers, and determined that 2 percent carried a variant of the ABCC11 gene, which led them not to have body odor.

“This key gene is basically the single determinant of whether you do produce underarm odor or not," study co-author and genetic epidemiologist Ian Day told Live Science.

Researchers have hypothesized that the smell-free gene variant leads the body to produce fewer amino acids while it generates sweat — and that these amino acids cause rapid bacteria growth, which releases the smell we know as body odor.

"The characteristic human axillary odor is formed by bacterial action on odor precursors that originate from apocrine sweat glands. Caucasians and Africans possess a strong axillary odor, whereas many Asians have only a faint acidic odor," a 2010 study published in the Journal of Investigative Dermatology reported. These apocrine sweat glands are located near hair follicles, like those in your armpits and groin, according to the Mayo Clinic.

The same gene also determines the consistency and stench of your earwax, according to a 2010 study published by Oxford University Press. "Interestingly, people who produce the 'dry' version of earwax also lack a chemical in their armpits that bacteria feed on to cause underarm odor," reporter Tia Ghose wrote on Live Science.

Who carries the smelly gene?

The 2013 study's authors discovered that your ethnicity can help predict whether you carry the odorless gene variation.

"Over 97 percent of people who are of European or African descent have the smelly underarm sweat gene," Next Shark stated in a piece about the study's results.

Meanwhile, almost all Koreans, most East Asians, and 30 to 50 percent of Southeast Asians, people from the Pacific Islands, Central Asia, Asia Minor, and indigenous Americans were blessed with the stench-free gene variant.

"No one knows exactly why gene prevalence varies so much between populations," Live Science reported, "but its absence in East Asia suggests that being stinky was evolutionarily selected against there over the last several thousand years, [Day] said."

D.O. for B.O.?

Day also observed that nearly three quarters of the lucky European subjects who carried the odor-free gene still used deodorant on a daily basis, which he believed was unnecessary, and primarily due to social pressure.

“They’re spending their money, exposing their skin to what may in a few instances not be good for their skin,” he told Live Science. “It sort of suggests to me that there are a lot of conformists around.”

While deodorant use has been popularized in Western Europe and the United States as a personal hygiene ritual no more optional than brushing your teeth or washing your hands, in other parts of the world, it is less commonplace because people simply smell better.

"We believe that these people simply follow socio-cultural norms,” Day told Motherboard. “This contrasts with the situation in North East Asia, where most people do not need to use deodorant, and they don't.”

[h/t Next Shark]