For most, putting on deodorant is a necessary ritual on par with brushing teeth or washing hands. But for people who produce no armpit stench, it is totally unnecessary.
Despite that, nearly three-quarters of those people still use deodorant daily, a new study finds.
The findings, published today (Jan. 17) in the Journal of Investigative Dermatology, show just how much a person's daily life is dictated by what's considered normal.
"They're spending their money, exposing their skin to what may in a few instances not be good for their skin. It sort of suggests to me that there are a lot of conformists around," said study co-author Ian Day, a genetic epidemiologist at the University of Bristol. [10 Odd Facts About the Female Body]
Several years ago ago, scientists discovered that a gene called ABCC11 determined whether people produced wet or dry earwax. Interestingly, people who produce the "dry" version of earwax also lack a chemical in their armpits that bacteria feed on to cause underarm odor.
"This key gene is basically the single determinant of whether you do produce underarm odor or not," Day said.
While only 2 percent of Europeans lack the genes for smelly armpits, most East Asians and almost all Koreans lack this gene, Day told LiveScience.
No one knows exactly why gene prevalence varies so much between populations, but its absence in East Asia suggests that being stinky was evolutionarily selected against there over the last several thousand years, he said.
The new findings came as a surprising twist on a larger study investigating chemical exposures in 6,495 women and their babies in Britain. Researchers took blood samples (which contain genetic material) from the women and asked them what types of hygiene products they used daily. As a result, the researchers could investigate how genes related to product usage.
About 98 percent of the women had the gene for smell-producing armpits. Of those, 95 percent used deodorant on a regular basis.
But of the the 117 non-odor producing women, over three-quarters still used deodorant daily. That suggests the majority of women are using a product every day, when they have no need to, Day said.
Though the team didn't look at men, they think the results should generalize. (Other studies have found that men in general are slightly less fastidious in their deodorant use, Day said.)
Because the study didn't intend to look at deodorant use, the researchers can't tease out why smell-free women continue to slather on the odor-reducing product. But one possibility is that social pressure or conformity plays a large part in some of our most common hygiene routines, Day said.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.
Tia is the managing editor and was previously a senior writer for Live Science. Her work has appeared in Scientific American, Wired.com and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.