Kissing does not invalidate Wudhu'
Question :
Does kissing invalidate Wudhu"?
Answer:
It is reported on the authority of 'A'ishah, may Allah be pleased with her, that the Prophet kissed one of his wives, then he went out to prayer without performing Wudhu'. This Hadith makes the ruling clear on touching and kissing a woman: Does it invalidate Wudhu' or does it not invalidate Wudhu"? The scholars may Allah have mercy on them - have disagreed on this; some of them said that touching her in any circumstances invalidates ablution, while others said that touching her with desire invalidates it, while if it is without desire, it does not. Others said that it does not invalidate Wudhu' under any circumstances, and that is the most authoritative position. This means that when a man kisses his wife or touches her hand or hugs her, without emitting any fluid, then his Wudhu' is not invalidated, nor is that of his wife. This is because the basic principle is that the Wudhu' remains as it was until some evidence is brought to show that it is invalid, and no evidence has been shown - neither in the Book of Allah nor in the Sunnah of the Messenger of Allah that touching a woman invalidates Wudhu'. Therefore, touching a woman or kissing or hugging her even without any covering, or with desire does not nullify Wudhu'... And Allah knows best.
Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 2 Pages 79-80