You Share 80 Million Bacteria When You Kiss Someone, Research Finds

November 17, 2014 | Prachi Gupta

Remember back in second grade when you didn’t so much as hold hands with another kid cause he probably had cooties? Well, congratulations on getting over that fear, but now science says your cootie theory wasn’t totally invalid. Science Daily reports that as many as “80 million bacteria are transferred during a 10 second kiss,” the findings of a study published in Microbiome. What’s more interesting is that people who kiss at least nine times a day share “similar communities of oral bacteria.”

Researchers from TNO and Micropia in the Netherlands studied the oral bacteria of 21 couples and found that the salivary bacteria in our system isn’t just influenced by our physical environment, but also by individuals whom we are closest to. From lead author Remco Kort:

“Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90% of known cultures. Interestingly, the current explanations for the function of intimate kissing in humans include an important role for the microbiota present in the oral cavity, although to our knowledge, the exact effects of intimate kissing on the oral microbiota have never been studied. We wanted to find out the extent to which partners share their oral microbiota, and it turns out, the more a couple kiss, the more similar they are.”

The researchers surveyed the couples about their kissing habits, and then took oral swab samples to get an idea of what their saliva microbiota composition was like. They then had one person in each couple take a probiotic drink containing specific bacteria and “found that the quantity of probiotic bacteria in the receiver’s saliva rose threefold.” They extrapolated that 80 million number from these findings.

Interestingly, though, the researchers “found that while tongue microbiota were more similar among partners than unrelated individuals, their similarity did not change with more frequent kissing, in contrast to the findings on the saliva microbiota.”

It’s a fun fact to share with your special someone before you swap saliva with him again.

(Image: Anna M)