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A single kiss can share up to 80 million types of bacteria, but may also help to keep you healthy, Dutch scientists said.
Researchers from the Netherlands Organisation for Applied Scientific Research (TNO) studied 21 couples to determine the health effects of kissing. They found that the mouth is home to 700 million different bugs but that some are more easily shared through kissing than others, the BBC reports.
The scientists leading the investigation, Professor Remco Kort, said that couples who kissed more than nine times a day were more likely to share saliva. He said: "French kissing is a great example of exposure to a gigantic number of bacteria in a short time.But only some bacteria transferred from a kiss seemed to take hold on the tongue."
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He added: "Further research should look at the properties of the bacteria and the tongue that contribute to this sticking power. These types of investigations may help us design future bacterial therapies and help people with troublesome bacterial problems."
The human body contains millions of bacteria, which together make up the body's "microbiota" – a complex system that is designed to help digestion and ward off illness. Sharing germs through kissing may actually be an evolutionary development that helps aid the body's ability to defend itself, the TNO scientists suggested.
Biologists have long warned that the modern obsession with cleanliness and hygiene may be behind the current upward trend in allergies and health problems, the Daily Mail reports.
One immunologist at University College London, Professor Graham Rook, has even said that picking food up off the floor, owning a dog and kissing relatives could help prevent allergies and improve the body's resistance to illness.
"When the immune system is not needed it should get turned off completely," he told the Daily Mail. "What happens these days is that often it is on a constant state of alert and it is not turned off completely. It will do something completely pointless like attacking grass pollen wafting past in the breeze, or attacking the neighbour's cat when it happens to walk past, then you are going to have allergic problems."
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