Scientists have demonstrated that boys (well, men) really do have cooties (a simplified term for bacteria) that can spread to girls (OK, women) by kissing them.
In fact, a 10-second "intimate kiss" can transfer a whopping 80,000,000 bacteria from one mouth to another, according to a new report in the journal Microbiome.
FOR THE RECORD
An earlier version of this post said one volunteer's claim of kissing his partner 50 times a day would add up to 500 minutes of kissing. It would be 500 seconds, or 8 minutes and 20 seconds.
A team of Dutch researchers recruited 21 couples who happened to be visiting the Artis Royal Zoo in Amsterdam on a summer day. All 42 volunteers (whose ages ranged from 17 to 45) allowed the researchers to wipe their tongues with a cotton swab several times. They also agreed to spit into sterile tubes and answer questions about their kissing habits.
Then the volunteers engaged in some public displays of affection (a 10-second kiss "involving full tongue contact and saliva exchange") and had their tongues swabbed again. According to the bacterial analysis, a fresh kiss barely budged the similarity index value. That suggests that the overlap in tongue bacteria is probably "a long-term effect of couples living together" – sharing meals, toothpaste and other items from daily life.
A single kiss had no immediate effect on the composition of bacteria in the saliva samples, the researchers found. But swapping spit certainly entails swapping bacteria as well. The more often a couple kissed, the more similar the bacteria in their saliva samples. The scientists calculated that couples had to kiss at least nine times a day to achieve an MH value below 0.5.
And here's a bonus finding: The men said they kissed their partners an average of 10 times a day, while the women recalled kissing only five times a day. The researchers concluded that the men were most likely exaggerating the frequency of their romantic encounters. Most egregiously, one male volunteer said he averaged 50 intimate kisses per day. The researchers declared this estimate "unrealistically high." Besides, his partner said they kissed only eight times per day.