How Many Germs Are Exchanged Each Time You Kiss

WARNING...This might make you a little more selective about who you swap spit with.

What’s in a kiss? About 80 million microbes, apparently. Gross but true; that’s how many bacteria get transferred during the typical lip lock, according to a new study published in the journal Microbiome.

Researchers were curious about why humans are the only animal species that have full-tongue mouth-to-mouth contact. One theory says that exchanging saliva helps couples determine compatibility, while another holds that sharing bacteria can boost the immune system.

Since no previous study looked into how kissing changes mouth microbes, the study authors decided to take the lead. They monitored the kissing behavior of 21 couples, finding that one 10-second French kiss transferred 80 million germs from one partner to the other. They also discovered that the more often partners reached first base, the more likely they were to have a similar microbial profile colonizing their tongues. (So apparently, you and your guy do become more alike the longer you stay together!)

But before you freak out and never swap spit again: The researchers didn’t come to any conclusions about the implications of so many oral germs being exchanged. Instead, they called for more studies to look into why certain microbes, such as those on the tongue, colonize and grow, while microbes found in saliva tend not to stick around. In the meantime, we suggest using the research as a cool conversational tidbit to liven up an upcoming holiday party or draggy date. Or use it as pillow talk before kissing your partner—as long as they aren't a serious germaphobe.