Here’s How Many Bacteria You Exchange Through One Kiss

A study in the journal Microbiome found that a 10-second French kiss can spread 80 million bacteria between mouths. Eighty million may sound scary, but these bacteria may actually benefit your body.

Scientific Research in the Netherlands required 21 couples to participate in a study on French kissing. Their tongues were swabbed and saliva collected before and after a timed 10-second French kiss.

Interestingly, they found the bacteria on the tongues of couples were more similar than of two strangers. “Apparently, being with somebody for an extended amount of time and having a relationship leads to a similar collection of bacteria on the tongue,” said Professor Remco Kort, lead researcher, Netherlands Organisation for Applied Scientific Research.

To find how similar the shared bacteria were, the researchers did one more test. One person in the couple drank a probiotic yogurt drink containing bacteria called Lactobacillus and Bifidobacteria and waited awhile. Then, the couple shared a 10-second French kiss. The researchers took a sample of the bacteria in the mouth of the partner who hadn’t had any probiotic yogurt. What the researchers found was that the volume of bacteria transferred to the other partner was on average 80 million bacteria!

The research team also found out through questionnaires that the more often a couple kisses, the more bacteria they share. Dry, prudent kisses only transfer 1,000 bacteria and a French kiss will give millions of bacteria!

Even though bacteria in the saliva changed quickly after a kiss, the bug populations on the tongue remained more stable.

“French kissing is a great example of exposure to a gigantic number of bacteria in a short time. While 80 million bacteria being transferred in just one kiss sounds scary, it is in fact probably a good thing, acting as a form of immunization and building resistance from exposure to different microorganisms,” says Professor Remco Kort.

“If you look at it from this point of view, kissing is very healthy,” added Prof Kort.

Would you like to know how much bacteria you and your partner are sharing? There is a “Kiss-o-meter” set up in Amsterdam based on this research that will rate your kisses: Micropia. They will give you a read out of the microorganisms you’ve exchanged.