Scientists Have Discovered That A 10-Second Kiss Passes On 80 Million Bacteria

Here's something to think about next time you pucker up.

Have you ever thought about how gross a kiss actually is?

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A group of scientists from the Netherlands has. And then, because they're scientists, they went and did an experiment to find out more.

Professor Remco Kort, from the Netherlands Organisation for Applied Scientific Research, and his team got 21 couples to fill in a questionnaire. Scientists then took samples from the couple's tongues and saliva, and then analysed the samples to see what bacteria they could find.

The researchers discovered that a single kiss passes on around 80 million bacteria.

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In one part of the experiment the scientists got couples to kiss for 10 seconds, before getting one half of each couple to drink a probiotic yoghurt drink containing known bacteria, and then going in for another 10-second kiss. Yum.

They identified Lactobacillus and Bifidobacterium, two bacteria from the probiotic drink, in most of the partners who hadn't actually drunk it, and estimated that 80 million bacteria were passed between the partners during the kiss.

They also found exactly how much kissing it takes before couples were more likely than not to share salivary bacteria.

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The scientists took samples from the participants' tongues and their saliva.

Your mouth is home to around 700 different types of bacteria. Kort and his team discovered that on average the bacteria in your mouth is more similar to your partner's than a random, unrelated person, which makes sense.

But they also found differences between the extent to which the bacteria on your tongue and in your saliva match up with your partner's. It seems that your salivary bugs are more changeable, but those on your tongue like to stay put.

The researchers found that at least nine kisses a day led to couples sharing more salivary bacteria than not. In general, more kissing and a shorter time since the last kiss was related to the couple sharing more bacteria in their saliva.

But when it came to tongues, though couples were more likely to have similar bacteria, it didn't seem to have anything to do with kissing. So while kissing does transfer bacteria, that bacteria doesn't necessarily end up on your tongue.

Happy smooching!

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