Locking lips spreads more than just love. A healthy dose of microbes are also swapped between kissing couples, according to a study published today (November 17) in Microbe. Researchers in Amsterdam swabbed the mouths and collected saliva from 21 couples visiting a zoo in the city both before and after they shared 10-second kiss. They found that the couples tended to have similar microbes inhabiting their mouths, likely because they share kisses, food, and space on a regular basis.