Scientists in the Netherlands recruited 21 couples for the study. The researchers gathered swab samples to analyze oral bacteria on the tongue and in saliva. The volunteers were also asked to fill out questionnaires about how frequently they kissed.
In the second part of the study, the researchers had one person from each couple consume a probiotic drink with specific types of bacteria. They then asked the couples to kiss, after which they analyzed which types and how many bacteria from the drink were transferred.
The results of the study were two-fold. The researchers found that as many as 80 million bacteria could be transferred during a 10-second kiss. They also found that couples that kissed at least nine times a day were more likely to have similar oral bacteria.
Another finding was that 74 percent of the men in the study said they kissed their partner more frequently during a day than the woman remembered. Men reported an average of 10 kisses a day, while the women said it was more like five times a day.
The study’s findings, published in the journal Microbiome, suggest that oral bacteria may be transferred more easily than previously thought.
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