One Kiss Spreads 80 Million Bacteria, New Study Says

A ten-second kiss can transfer 80 million bacteria, a study published in Microbiome Monday shows.
“Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90 percent of known cultures,” said Remco Kort, who led the research. He is a professor of microbial genomics at Amsterdam’s VU University.
Researchers investigated 21 couples by asking them to fill out questionnaires, which include their self-reported kiss history.
The result shows the more frequently they kiss, the more similar the microbiota in their saliva is likely to be.
In order to develop similar microbiota, “frequent and recent bacterial exchange" is required. This means that similar microbiota profiles are usually found in couples who have a relatively high frequencies of intimate kissing.