Thank you for your question. Kissing is a least risky sexual activity. The only STI one needs to be concerned about is Herpes (HSV 1 & 2). It’s important to note that many people have the herpes infection and people are embarrassed talking about it considering the stigma around it. If you’re concerned about herpes and you think that you or your partner may have it, its best to have an honest discussion with your partner and discuss ways to prevent its spread. Consult your health care provider would be an added advantage.
One way to prevent is to be watchful and look out for symptoms that indicate that you are likely to have an outbreak such as burning and painful sensation, itching or tingling feeling in and around your mouth area. It if any of these are appearing, it might be signs of herpes. It is recommended to avoid kissing if you or your partners have sores on the lips or mouth or if you have an active oral infection (such as a herpes outbreak).
Having a chat with your health care provider would help in taking medications that can reduce the chances of transmission and management of a herpes outbreak.
Very rarely kissing may result in transmission of HPV and syphilis provided either of the partners have a wart or a syphilis lesion on their mouth. Majority of the STIs can be easy treated and managed so the key is to get tested and seek treatment.