Answered by Shaykh Faraz Rabbani
Does saliva exchange (through kissing) break wudu?
Answer:
Walaikum assalam wa rahmatullah,
No, exchange of saliva through kissing does not invalidate one’s wudu. However, it would be recommended to renew one’s wudu (particularly before prayer), in order to avoid the difference of opinion of those schools (such as the Shafiis) who deemed wudu to break through direct contact with someone of the opposite sex. [Shurunbulali, Maraqi]
And Allah alone gives success.
Wassalam,
Faraz Rabbani