A recent study has suggested that certain forms of close physical intimacy may temporarily improve immune function by increasing exposure to shared oral bacteria.
Researchers from the University of California, San Francisco found that couples who exchanged saliva more frequently tended to have greater diversity in their oral microbiome and stronger short-term immune responses.
The study followed 178 adult couples over a four-month period. Researchers monitored immune activity, stress levels, and changes in oral bacteria through regular testing.
According to the findings, participants who engaged in more frequent kissing and other saliva-sharing activities had higher levels of beneficial oral bacteria. They also experienced fewer minor seasonal illnesses during the study period.
Scientists further observed lower cortisol levels, a hormone linked to stress, among long-term couples who regularly showed physical affection.
The study also found that these couples appeared to recover better overnight compared to those who expressed less physical affection.
According to the researchers, repeated exposure to a partner’s microbiome may help train and strengthen the body’s adaptive immune system over time.
They explained that this process is similar to how regular exposure to different environmental factors can help improve overall immune resilience.
The findings add to growing scientific research examining the relationship between physical intimacy, stress reduction, shared bacteria, and long-term health.
Researchers noted that while the results are promising, more studies are needed to better understand the long-term effects of shared microbiomes on immune health.
