Locking lips releases 80 million bacteria

A ten second kiss – long enough to draw looks on public transport and just the right amount of time a Hollywood flick needs to take full advantage of an emotive soundtrack – transfers 80 million bacteria between two people, a new study has found.

According to a study of 21 couples published in the journal Microbiome, the answer has to what’s in his (or her) kiss can’t be found in a Cher song , it was in a laboratory where couples swapped spit for science that the discovery was made.

Studies suggest the mouth is home to more than 700 different types of bacteria - but the report reveals some are exchanged more easily than others.

Each couple had their mouths swabbed and spit to catalog measure the bacteria in their mouths. Even before kissing, the couples had similar mouth bacteria.

After the strictly-timed kiss, one member of the couple then drank a probiotic drink, containing an easily identifiable mixture of bugs.

On the couple's second kiss, scientists were able to detect the volume of bacteria transferred to the other partner - on average 80 million bacteria in a single 10-second kiss.

GALLERY: 15 things she's thinking when you're naked

The researchers focused on Lactobacillus and Bifidobacteria, which together usually make up only about 0.15 percent of the bacteria in human saliva and 0.01 percent of the bacteria on the tongue.

But after the second kiss, the Lactobacillus and Bifidobacteria in the person on the receiving end rose substantially — up to 0.54 percent in saliva and 0.49 percent on the tongue. This led them to the estimate that each smooch carries 80 billion bacteria.

“There are a number of studies that show if the diversity in bacteria increases—more different types of species—this is a good thing,” Study Remco Kort says. Kissing might also act as a form of immunisation, he adds, allowing you to build up resistance from exposing yourself to more microorganisms. “If you look at it from this point of view, kissing is very healthy.”'

"Kissing is an enormous stimulant to certain brain systems,” says Dr Helen Fisher, a professor of anthropology at Rutgers University in the US and author of Anatomy Of Love.

“A huge amount of biological information appears to be sent to your brain during a kiss. This may be why a kiss with a stranger immediately turns you on or off."

"Kissing may be an evolutionary mechanism. It seems women are more attracted to men who have opposing immune systems, which would provide the best protection for offspring."