It is reported on the authority of A'ishah, may Allaah be pleased with her, that the Prophet Sallallaahu alayhi wasallam kissed on of his wives, then he went out to pray without performing Wudhu'. [ Abu Dawud no.178-179, At-Tirmidhee no.86 and Ahmad 6: 2, 10, 207.]
This Hadith makes the ruling clear on the touching and kissing a woman:
Does it invalidate Wudhu' or does it not invalidate Wudhu'?
The scholars - may Allaah 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, them 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 brougth to show that it is invalid, and no evidence has been shown - neither in the Book of Allaah nor in the Sunnah of the Messenger of Allaah Sallaahu alayhi wasallam - 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 Allaah knows best.