In 1968, a metaphor of the human body emerged in Scientific American that endures to this day. It called the human body an ecosystem. Within this ecosystem, the author wrote, are several “ecological niches.” The forearm is dry like the desert. The scalp is airy like the cool woods. And then the armpit, the lowliest of all human body parts, is a ‘tropical forest.’ ”

Hot and humid, the armpit is populated by bacteria and cursed with creating a noxious odor. That smell, however, has proved lucrative. Today, more than 90 percent of Americans use some sort of armpit cosmetic, creating a worldwide deodorant bonanza worth $18 billion.

But what if part of that industry is predicated on a notion that smells fishy?

New research published in the Archives of Dermatological Research suggests antiperspirants actually increase the levels of the odorous bacteria populating the armpit, which “could lead toward an altered, more unpleasant underarm odor,” lead author Chris Callewaert of Belgium’s Ghent University told The Washington Post in an email.

This smell can be masked with deodorant. Or the sweat can be stopped with antiperspirants that contain an aluminum-based compound, which temporarily plugs sweat ducts. But what effect, if any, do such techniques have on the bacteria itself?

Researchers found that the diversity of bacteria in the armpit increased, but their abundance decreased. “The armpit microbiome changed considerably when starting or stopping the use of deodorants and antiperspirants,” Callewaert said. “In the case of the antiperspirants, the dominance changed toward the ‘smelly’ actinobacteria

“The deodorant-antiperspirant industry should investigate what their products do to the underarm microbiome,” or community of microscopic organisms living on our skin, said Callewaert, who has a “Dr. Armpit” website. Antiperspirants “should not enhance the odor-causing bacteria, but rather ‘steer’ towards a non-odor-causing microbiome,” he said.

Observers, however, have already highlighted one problem with Callewaert’s research: the small sample size. In all, only nine people – eight of whom stopped using deodorant or antiperspirant for one month – were tested. “The sample size is rather small,” Callewaert conceded in an interview with Real Clear Science. “However, we see consistent outcomes.”

Still, it’s not time for sweeping conclusions yet – and it’s unlikely the study will bring about the collapse of the antiperspirant trade. Dr. Armpit wants to conduct more studies.

“Don’t get me wrong,” Callewaert said, “there is no reason to ban all deodorants and antiperspirants. There is nothing wrong with a higher diversity in your armpit.”

Only subscribers are eligible to post comments. Please subscribe or to participate in the conversation. Here’s why.

Use the form below to reset your password. When you've submitted your account email, we will send an email with a reset code.