Researchers at TNO in the Netherlands recruited 21 couples and sampled the bacteria living on their tongues and in their saliva before and after they kissed.
A single ten-second intimate kiss transferred an average of 80 million bacteria from one partner's mouth to the other's. Couples who reported kissing often had more similar saliva bacteria than couples who kissed less, though a single kiss did not make a couple's bacteria measurably more alike.
Tongue bacteria turned out to be a longer-term fixture, shaped by shared diet and lifestyle more than by any single kiss, while saliva bacteria were more like a transient visitor that came and went with recent contact. The researchers suggest frequent kissing nudges couples toward a shared oral microbiome over time, built up kiss by kiss rather than fixed after the very first one.
Read the original study
Kort et al., Microbiome, 2014 · doi.org/10.1186/2049-2618-2-41
80 million reasons to brush first.
Source
- Kort, R., Caspers, M., van de Graaf, A., van Egmond, W., Keijser, B., & Roeselers, G. (2014). Shaping the oral microbiota through intimate kissing. Microbiome, 2, 41. https://doi.org/10.1186/2049-2618-2-41