For most people, putting on deodorant is a necessary ritual on par with brushing teeth or washing hands. But for those who produce no armpit stench, it is totally unnecessary.
Despite that, more than three-quarters of those people still use deodorant at least once a week, a new study finds.
The findings, published in the latest issue of 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.
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. The researchers estimated that about $32 per person each year -- or a total of $14.3 million -- is spent on deodorants by people who don't produce odor.
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.