Answered by Shaykh Faraz Rabbani
Question : Do the following break one’s ablution: smoking, breastfeeding, nakedness, kissing the opposite gender, a female removing her scarf, and washing impurity of a baby?
Answer : 1. Smoking is either blameworthy or prohibited. However, it does not affect the validity of one’s wudu.
2. Nakedness, washing a baby’s impurity, taking off one;s scarf, and and breastfeeding do not break wudu either.
3. No, exchange of saliva through kissing does not invalidate ones wudu. However, it would be recommended to renew ones 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]