When you kiss someone, you don’t only show your affection for them; you’re also spreading millions of bacteria with that person — 80 million, to be exact, according to a recent study published in the journal Microbiome.

Scientists from the Netherlands headed to Amsterdam’s Artis Royal Zoo, and asked 21 couples to participate in the study. The couples had their mouths swabbed before and after sharing a kiss.

To monitor the bacterial transfer, the researchers had one individual consume a probiotic yogurt drink before sharing the kiss. That way they could look for the specific bacteria found in the drink.

And the researchers found another interesting (and a bit gross) statistic: the couples shared similar oral bacteria.

In other words, two strangers aren’t likely to have similar bacterial colonies, but two individuals in a couple are. It makes sense, given they’re swapping 80 million bacteria on the regular.

All of this might sound bad, but it’s actually quite normal. There are trillions of microorganisms in your body, and some diversity is a positive thing.

Time quotes one of the scientists in the investigation who says, “There are a number of studies that show if the diversity in bacteria increases … this is a good thing,” because it helps strengthen your immune system.

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