It should be quite clear that in principle, contacts between men and women are not totally rejected; rather, recommendable so long as they abide by the Islamic guidance in this regard.
However, this by no means calls for transgressing the limits and forgetting about the nature of both sexes. It is prohibited for man and woman who are non-mahrams (i.e., those who are not close relatives) to shake hands with desire, hug or kiss each other even if they are engaged.
Muslims we are not to hug or kiss non-mahram members of the opposite sex at any time for to do so is forbidden by Islam. The reason for this being that Allah wants to save us against weaknesses inherent in our own nature. For such actions may or may not be preludes to fornication. Because fornication is considered a grave sin and an abomination in the sight of Allah, Allah wants us not even to come close to it. He said, “Do not even go near fornication, for it is an indecent thing and an evil way.” (Al-Isra’: 32)