By Alphonso Van Marsh

AMSTERDAM (CBS NEWS) – Scientists in the Netherlands say new research shows couples who French kiss share millions of bacteria – and the more often they kiss, the more similar their saliva becomes.

The study, published the American scientific journal Microbiome, looked at 21 couples and measured how many microbes they exchange.

“In a single kiss of ten seconds, 80 million bacteria are transferred – on average – from one person to the other,” says Remco Kort, principal scientist with Netherlands Organisation for Applied Scientific Research who collaborated with Amsterdam’s Micropia Museum for the study. The museum claims to be the first dedicated to the science of microbes.

Study scientists asked one partner to drink a yogurt solution that contained bacteria not usually found in the mouth, then had the couples kiss for ten seconds.

“That allowed us to make an estimate of how many bacteria were transferred from one person to another,” Kort says.

The researchers took samples from the tongue and saliva of the couples before and after they kissed. The study found that in addition to French-kissing couples’ saliva appearing to seem the same, the bacteria on the tongues of the couples become more similar compared to samples from random people. The study conclusions cite other factors, such as couples sharing the same diet or toothpaste, that can affect the bacteria composition. Kort says a significant difference in height between French-kissing partners can result in a greater exchange of saliva – downward – to the shorter participant.

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