I never kissed or been in relationship so I don't know what I like. But kissing in general feels icky and unhygienic, I never kissed so I can only imagine.
If your partner is generally healthy, it will likely be a good thing as they'll be sharing their personal commensal organisms with you; however, there is some evidence that someone that is consistently exposed to pollution and toxins (i.e. live near a factory and/or a busy road) will have poorer microbiome health which might be passed on to intimate partners.
