Maran writes (ibid.) that this even applies to a sister. One may not hug a sister, and one that does so, is called a fool. A father may hug his daughter, and a son my hug his mother.
These Halakhot are not very well known, but are extremely important, and must be handled for carefully.
If one is in a situation where a woman attempts to shake his hand for business matters, he may NOT shake her hand, even if it will embarrass the woman. However, woman are permitted to kiss scholars' hands, because it is in a way of awe and respect, rather than a way of love and attraction.
