Just how many germs do we swap with French kissing?

A kiss is a kiss to some people, but some kisses are much more intimate than others–in more than just the emotional sense! French kissing,…

Here’s how many bacteria spread through one French kiss. (Shutterstock)

A kiss is a kiss to some people, but some kisses are much more intimate than others–in more than just the emotional sense! French kissing, for example, is much more than just a polite touch of the lips.

French kissing, or deep kissing in which participant’s tongues connect, is considered one of the pre-cursors to sex, and creates both a physical and emotional connection between partners. This type of kissing is considered especially erotic, but it might just lose its appeal the more researchers uncover about just how “intimate” French kissing really makes you.

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According to new data from researches in The Netherlands, a 10-second French kiss is enough to transfer 80 million bacteria from one person’s mouth to another’s. Over time, this can actually change the microbiome in a person’s mouth; couples who kiss at least nine times a day have similar bacteria colonies on their tongues.

“During a kiss, you get exposed to many bacteria, but only a minor fraction of them are able to colonize the human body,” said Remco Kort, a co-author of the stud, to Live Science. “[The tongue], is where the bacteria find a niche, and they colonize there over longer periods of time.”

What this means exactly for individuals is not clear yet, as the impact of the human microbiome on health is a field just starting to develop.

The most notable research has to do with the microbiome in the intestine; experts have concluded that fecal transplants–the transplantation of health fecal material into an unhealthy colon–can drastically improve and individual’s health and can help remedy some chronic intestinal conditions.

The microbiome in the intestine is just a small portion of the organisms that make up the human microbiome, however. This community of pathogens exists all over the body, and how it changes a person’s health is currently under investigation.

“Before birth, we’re all more or less sterile—we have no microbes,” explain materials from the University of Utah. “Within a few years, we’re covered in thousands of different species of microbes, and they colonize every millimeter of the body that’s exposed to the outside world. By the time we enter kindergarten, we have vastly different populations living in the different habitats around our bodies. Even as adults and into old age, our microbiota continue to shift.”

Because environment influences the human microbiome as much as things like hormone fluctuations and diet, many experts feel the human microbiome is unique to the individual. With so many millions of different microscopic organisms out there, it seems entirely possible that, like a fingerprint, every person’s microbiome is different.

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That couples can develop similar microbiomes in the mouth may actually prove to be some form of adaptation that was advantageous to our ancestors for survival. Because procreation was more of a necessity for our ancestors rather than a desire, it could be the sharing of the mouth microbiome led to improved immunity for one or both partners.

Theories as why French kissing and a changing mouth microbiome may be beneficial are, at this time, just speculation. Researchers indicate more studies are needed to understand how the mouth microbiome–and the human microbiome in general–influence human health.