A passionate kiss shares much more than intimacy. A single 10-second smooch can transfer tens of millions of bacteria from one partner to the other. That’s the finding from a study in the journal Microbiome. [Remco Kort et al, Shaping the oral microbiota through intimate kissing]
More than 700 different bacteria are estimated to live in the human mouth. To find out how macking mixes microbes, Dutch scientists asked 21 couples to French kiss.
 
Intimate partners already have more of the same bacteria in their mouths than do unrelated individuals, because of the couple’s shared habits and environment. But kissing really expedites the bacterial blending.
 
As part of the study, one member of the couple consumed a probiotic yogurt drink loaded with certain bacteria. Saliva samples and tongue swabs revealed that after the couples puckered up, about 80 million bacteria from the drink moved mouth to mouth.
 
The salivary bug exchange was extensive but the work does not yet tell us why certain swapped bacteria either stuck around or were more transient. Answering that question could help with future medical interventions aimed at microbes.
 
What the research did show: although the bacteria in saliva were easily altered, bacteria living on tongues tended to stay put. Unlike certain frog-princes, those critters were less prone to change because of a mere kiss.
 
—Dina Fine Maron
 
[The above text is a transcript of this podcast.]