Couples who live together share a lot of things: beds, bathrooms, food, toiletries. But one thing they might not expect to share? Skin bacteria.
In a study published Thursday in mSystems, an open-access journal of the American Society for Microbiology, researchers studied the skin microbiomes of 10 sexually active, heterosexual couples living together.
A microbiome is a mini-ecosystem of bacteria, fungi, viruses and other microorganisms living on and in the body. Each square centimeter of skin hosts between one million and one billion microorganisms, according to the study.
After analyzing 330 skin swabs collected from 17 parts of the body on each participant, the researchers found that each person significantly influenced the microbial communities on a lover’s skin.
In fact, computer algorithms relying on microbial data were able to accurately match couples with up to 86 percent accuracy.
“The most surprising aspect of the study was that we could identify a microbial fingerprint common to cohabiting couples,” Josh Neufeld, co-author and a biologist at University of Waterloo, wrote in an email.
And the part of the body most likely to host a microbial community shared by a couple: the feet.
The study didn’t examine causality, but the researchers say it’s likely microbes are picked up from skin and bacteria in the home. Humans shed over one million biological particles every hour, and it’s particularly easy to pick up new microbes on the feet — in the shower shared with a partner, for instance, or walking barefoot around the home.