If you’re kissing passionately to stay warm, a new study shows that you could catch a cold. Not that it’s going to stop you, because making out is usually worth a little bout of the sniffles, but open-mouth kissing exchanges all kinds of bacteria. Which really shouldn’t come as a surprise.

After studying the mouths and kissing habits of 21 couples, Dutch researchers have found that 10 seconds of “French kissing” can transfer up to 80 million bacteria. The couples answered questions about how often they shared intimate kisses throughout the day, and then their mouths were swabbed. At that point, it was clear that significant others who participated in full tongue contact and saliva exchange at least nine times a day had “shared salivary microbiota.”

To find out just how much bacteria was being exchanged, one person in each couple drank a probiotic yogurt drink that contained identifiable varieties of bacteria not normally found in the mouth. The result was that after a 10-second, open-mouth kiss, the amount of bacteria increased by three times. From there, the researchers came up with the number of 80 million bacteria transferred for regular kissers.

The good news is that kissing is actually good for you. That kind of intimacy improves your mental health and releases endorphins in your brain. “Kissing is very healthy,” according to one scientist, because the more bacteria we’re exposed to, the better our resistance becomes. Just make sure the other person isn't fighting a cold.

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