The Truth About Bacteria Exchange During Kissing

You've probably seen this claim floating around the internet: "More than 40,000 parasites and 250 types of bacteria are exchanged during a typical French kiss!" It's the kind of fact that makes you want to swear off smooching forever. There's just one problem—it's completely wrong.

Let's clear the air (and your conscience) about what's really happening when you lock lips with someone special.

The Real Numbers Will Blow Your Mind

Here's what actual science shows: A 10-second French kiss transfers approximately 80 million bacteria between partners. That's right—million, not thousand. This finding comes from a 2014 study published in the journal Microbiome, where Dutch researchers at TNO and Amsterdam's Micropia Museum studied 21 couples.

But wait, there's more. Your mouth isn't home to just 250 types of bacteria—it hosts over 700 different bacterial strains. Your oral cavity is essentially a thriving metropolis of about one billion bacteria at any given time.

So What About Those "Parasites"?

Here's where the myth completely falls apart: The claim confuses bacteria with parasites, which are entirely different organisms. Bacteria are single-celled microorganisms, while parasites are organisms that live on or in a host. There's no credible scientific evidence that you're exchanging parasites when you kiss someone.

The real story is about bacterial exchange—and it's actually fascinating rather than horrifying.

How Scientists Figured This Out

The research team used an ingenious method to track bacterial transfer. They had one partner drink a yogurt solution containing specific probiotic bacteria (Lactobacillus and Bifidobacteria) that aren't normally found in the mouth. After the couples kissed for ten seconds, scientists measured how many of those marker bacteria showed up in the other partner's saliva.

The result? A threefold increase in those specific bacteria in the receiver's mouth. Mystery solved.

Should You Be Grossed Out?

Before you vow to become a hermit, consider this: couples who kiss at least nine times a day develop similar oral microbiomes. Your mouth bacteria actually start to resemble your partner's bacteria over time.

And here's the kicker—this is probably a good thing. The bacterial exchange may help strengthen your immune system by exposing you to new microorganisms. It's like a workout for your body's defenses, except way more enjoyable than going to the gym.

The most similar bacterial communities are found on the tongue surface, while salivary bacteria require more frequent kissing to stay synchronized. If you haven't kissed your partner recently, your salivary microbiomes start to diverge.

The Bottom Line

The viral claim about 40,000 parasites is pure fiction—a game of telephone gone wrong. The real science is actually more impressive: 80 million bacteria, hundreds of different strains, and a complex microbial exchange that probably benefits your health.

So the next time someone tries to gross you out with the parasite myth, you can set them straight. Yes, kissing involves swapping spit and bacteria. No, you're not exchanging parasites. And yes, those 80 million bacteria are probably doing you more good than harm.

Now pucker up with confidence—armed with actual facts instead of internet myths.