Up To 80 Million Bacteria in a Single Kiss?

Necking, snogging, or sucking face, call it whatever you want but regardless, kissing (for 10 seconds) doesn't just swap spit, but also up to 80 million bacteria, a new study shows.

What's more, partners who kiss each other at least nine times a day share similar communities of oral bacteria.

"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," lead author Remco Kort said in a press release, "and it turns out, the more a couple kiss, the more similar they are."

Our bodies harbor more than 100 trillion microorganisms - the microbiome - all of which are vital for food digestion, synthesizing nutrients, and preventing disease. Our mouths alone are host to more than 700 varieties of bacteria, shaped by genetics, diet, and age, but also by the individuals with whom we interact.

Described in the study, published in the journal Microbiome, researchers from Micropia and TNO in the Netherlands studied 21 couples, asking them to fill out questionnaires on their kissing behavior, including how often they did it.

After taking swab samples of their saliva, the research team realized that the couples that kissed more frequently showed similar microbiota in their mouths.

Researchers tested the matter further via a controlled kissing experiment, in which a member of each of the couples had a probiotic drink containing specific varieties of bacteria. After an intimate kiss, the researchers found that the amount of probiotic bacteria in the receiver's saliva rose three-fold. They thus determined that during a kiss that lasts 10 seconds long, as many as 80 bacteria are transferred.

Given that tonsil hockey is a popular act of intimacy in over 90 percent of known human cultures, it may be safe to say that partners are sealing a lot more than they realize with each kiss.