A sweet kiss with a bacterial touch: a potential positive feedback loop involved in shaping the oral microbiota

The human microbiota —the collection of microorganisms living on and inside the body—plays a fundamental role in human health. While diet, genetics, and environment strongly shape microbiota composition, social interactions may also influence the microbial communities associated with the human body. Intimate kissing is a widespread human behaviour that involves close contact and exchange of saliva, providing an opportunity for direct microbial transmission between individuals. This article explores the hypothesis that intimate kissing can induce a reinforcing cycle – a positive feedback loop - that shapes and stabilizes the oral microbiota of partners over time. Neurobiological pathways, including the gut microbiota–brain axis, might reinforce this feedback loop. Current evidence is synthesized and a study design outlined to explore how kissing may lead to sustained microbial sharing and potential systemic effects.