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Give Me a Peck: All the Bacteria Transferred from ONE Kiss


It's the end of your romantic night out, and your date is dropping you off at your front door. You smile and flash them a beautiful look, hoping they receive the message. But then your mind goes to the moment you realize all the bacteria in a kiss. You are about to get thousands upon thousands of this person’s germs transferred to your mouth.

Before you swear this off for good, there are some health benefits to kissing your sweetie. But research led by Remco Kort, of TNO (Netherlands Organisation for Applied Scientific Research) and adviser to the Micropia museum of microbes in the Netherlands,  dove deep into the bacteria transferred in a kiss.

How Much Bacteria is in One Small Kiss?

The researchers noted some different factors are important for shaping our microbiota, including genetic relatedness, diet, and age. But our surroundings, including the individuals with whom we interact, also affect our microbiota. The team notes our mouths themselves contain over 700 varieties of bacteria, and these are also influenced by those we are closest to, such our romantic partners.

Remco Kort says as far as he and his colleagues know, “the exact effects of intimate kissing on the oral microbiota." They found out the extent to which partners share their oral microbiota, and it turns out, the more a couple of kisses, the more similar they are.

Kissing research

Kort and his team assessed 21 couples who completed questionnaires on their kissing behavior, including average intimate kiss frequency to further study how kissing affects oral microbiota. The team found, “Intimate kissing involves full tongue contact, and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90% of known cultures.”

The researchers cite a recent study detailing the importance of kissing in human mating, which proposes the “first kiss” serves to evaluate a potential love mate. This happens when bonding through chemical taste cues in the saliva, including the movement of the bacterial community on the exterior of the tongue.

After taking swab samples to determine the composition of each’s oral microbiota on the tongue and in the saliva, the researchers found that when couples intimately kiss at high frequencies, their salivary microbiota becomes similar. In fact, nine intimate kisses per day linked to couples having “significantly shared salivary microbiota.”

The total number of bacteria

If they wanted to quantify bacteria transfer, one individual from each couple drank a probiotic beverage with specific varieties of bacteria called Lactobacillus and Bifidobacteria.

Results showed the number of probiotic bacteria in the other individual’s saliva rose threefold, and during a 10-second kiss, a total transfer of 80 million bacteria, after kissing intimately. “This study indicates that a shared salivary microbiota requires a frequent and recent bacterial exchange and is, therefore, most pronounced in couples with relatively high intimate kiss frequencies,” write the authors.

Long effects of bacteria in a kiss

Another finding from the study reveals an essential role for mechanisms behind the selection of oral microbiota—particularly those on the tongue. Though tongue microbiota was more similar among partners than unrelated individuals, the similarity did not alter with more frequent kissing, which is in contrast to microbiota found in saliva.

The researchers further explain: “Our findings suggest the shared microbiota among partners can proliferate in the oral cavity, but the collective bacteria in the saliva are only transiently present and eventually washed out, while those on the tongue’s surface found a true niche, allowing long-term colonization.”

To calculate the number of bacteria transferred during a kiss, the researchers used average transfer values and assumptions related to bacterial transfer, kiss contact surface and the value for the average volume of saliva.

How to Avoid Some Bacteria in a Kiss

Besides ruining a kiss with bad breath, there are ways for you to avoid having so many bacteria in your mouth when you are getting ready to pucker up.

Keep up your daily dental hygiene

Maintaining your mouth clean is important for helping not spread more bacteria in a kiss. An effective daily dental hygiene routine helps you and your partner enjoy more smooching with fewer mouth bacteria coming in between you both. Brush and floss twice a day to keep your mouth ready for some intimate kissing.

Set up a dentist appointment twice a year

Visiting your dentist for a routine check-up helps to avoid any dental issues from coming between you and your sweetheart. Plan to see your dentist for a check-up at least twice a year to maintain a healthy mouth.

Lower Your Bacteria Count by Visiting Cabrillo Family Dental Care

Stop on by to our office for your preventative dentistry appointment and see how your teeth and mouth are doing before a significant date. Schedule a consultation with us today!