Buzz
The human mouth hosts 700 types of bacteria. Ever wondered how many germs you’re swapping when you kiss someone? A recent study published in the journal Microbiome provides the answer: in a 10-second kiss, 80 million bacteria are exchanged on average.
Researchers from the Micropia Museum in Amsterdam and TNO Microbiology and Systems Biology in the Netherlands explored intimate kissing, involving full tongue contact and saliva exchange, a practice common in over 90 percent of cultures worldwide. They asked 21 couples, aged 17 to 45, to fill out surveys covering their eating habits, kissing frequency, and the time since their last kiss. Then, they collected saliva and tongue samples to study the bacteria present. Results showed similar bacteria profiles among partners, likely influenced by shared habits like smoking, diet, and even toothpaste use.
To determine how many bacteria are passed during a kiss, one person from each couple drank a probiotic liquid containing Lactobacillus and Bifidobacteria, bacteria that typically make up 0.15 percent of saliva bacteria and 0.01 percent of tongue bacteria. After kissing, saliva and tongue samples were taken again. The analysis showed that the probiotic bacteria in the recipient’s saliva increased to 0.54 percent and 0.49 percent on their tongue. Remco Kort, lead researcher at the Netherlands Organisation for Applied Scientific Research, added that height differences between kissing partners could lead to more saliva being exchanged, especially if the shorter person receives more of the downward flow.
The study also revealed that couples who exchanged at least nine passionate kisses per day tended to have similar microbial communities in their saliva. However, these microbes didn’t remain for long if the French kissing stopped. The researchers noted, “Our findings suggest that the shared microbiota among partners is able to proliferate in the oral cavity, but the collective bacteria in the saliva are only temporarily present and eventually washed out, while those on the tongue’s surface found a true niche, allowing long-term colonization.”
A passionate kiss can transfer up to 80 million bacteria, but the Kiss-O-Meter at the Micropia Museum shows that a quick peck results in the transfer of only 1000 bacteria. So, pucker up!
