For the study, 21 couples visiting a zoo in Amsterdam were asked to lock lips for 10 seconds. Before the kiss, one member of each couple drank a yogurt drink containing specific strains of bacteria. After the kiss, the researchers swabbed the mouth of the partner who hadn't drunk the yogurt, and then did a bacterial count of the strains from the yogurt to arrive at the 80 million figure.
That certainly sounds icky. But before you swear off your sweetheart's lips, you should know that there's nothing inherently dangerous about transferring germs. In fact, the researchers say it can be a good thing.