A Single 10-Second Kiss Can Transfer 80 Million Bacteria

Gross: A single 10-second kiss can transfer 80 million bacteria

Kissing is disgusting: A poorly choreographed ritual of bad breath, awkward eye contact, and slobbery after-drool. Now, to make it even worse, a new study from the Netherlands has determined how many cooties move from one mouth to another during your basic smooch. And it's A LOT.

The study in the journal named Microbiome (of course) looked at the kissing habits of 21 couples as well as the microbial garden of their mouths. After answering a kissing questionnaire which explored behaviours from quick pecks to, you know, kissing with tongue, scientists swabbed the couples' oral cavities. Couples that kissed at least nine times a day had far more similarities in their salivary bacteria, which proved that exchanges were happening from mouth to mouth.

But researchers also wanted to know how much bacteria was being transferred, kiss for kiss. So they asked one member of each couple to drink some yogurt, then kiss, to see how much of its probiotic bacteria was transferred. The recipients ended up with three times as much Lactobacillus and Bifidobacteria in their mouths as they did pre-kiss, which works out to about 80 million bacteria per typical 10-second kiss.

This exchange of bacteria might offer some kind of evolutionary benefit, although we still don't know exactly what kissing is good for, according to one of the study's authors, Remco Kort, of TNO's Microbiology and Systems Biology department:

"Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behaviour unique to humans and is common in over 90 per cent 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."

So until we find out, pucker up and try not to think about what else you're planting on your partner's face. [WaPo]

Picture: Wallenrock/Shutterstock

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