This research paper investigates the influence of intimate kissing on the composition of the oral microbiota in 21 couples. Through questionnaires and analysis of tongue and saliva samples from a controlled kissing experiment, the study explores the similarity of microbial communities between partners and quantifies the bacterial exchange during a kiss. The findings reveal that while couples share a more similar microbiota on their tongue surfaces compared to unrelated individuals—likely due to long-term shared lifestyle and environment—the similarity of their salivary microbiota is directly correlated with the frequency and recency of intimate kissing. The study used marker bacteria from a probiotic drink to quantify the exchange, concluding that a single 10-second intimate kiss transfers an average of 80 million bacteria. This suggests that kissing facilitates a frequent but transient exchange of salivary bacteria, while more stable, long-term colonization occurs on the tongue.
The Impact of Intimate Kissing on Oral Bacteria
Partners Share Tongue Microbiota: The study found that partners have a significantly more similar bacterial community on the surface of their tongues compared to unrelated individuals. This similarity does not correlate with kissing frequency, suggesting it is a long-term effect of shared factors like diet, environment, and lifestyle.
Saliva Similarity Depends on Kissing Frequency: Unlike the tongue, the similarity of the bacteria in saliva is directly linked to kissing behavior. Couples who kiss more frequently have more similar salivary microbiota.
High Kissing Frequency is Key for Shared Saliva: To maintain a substantially shared salivary microbiota, a high frequency of at least nine intimate kisses per day is required. The similarity begins to decrease if samples are taken more than 1.5 hours after the last kiss.
An 80 Million Bacteria Exchange: In a controlled experiment where one partner consumed a probiotic drink, researchers calculated that an average of 80 million bacteria are transferred during a single 10-second intimate kiss.
Transient vs. Permanent Colonizers: The findings imply that bacteria transferred to the saliva are mostly transient and are washed out over time. However, some bacteria find a true niche on the tongue’s surface, allowing for long-term colonization and contributing to the stable similarity between partners.
Self-Reporting Discrepancies: An interesting behavioral finding was that 74% of men reported a higher intimate kissing frequency than their female partners (an average of 10 kisses per day for men vs. 5 for women), suggesting a tendency for male over-reporting.