halacha - Is there any reason a Jewish woman should not shake hands with a non-Jewish man?

My question refers to the custom of certain groups to prohibit all physical contact between men and women who are not spouses or related.

Although it is clear enough that Jewish men should not touch women for reasons of niddah, is there a sound, halachic reason that a Jewish woman could not touch a non-Jewish man?

I am referring to non-affectionate touch, such as sitting next to someone or passing. (May be better to avoid the example of "handshake" because that brings in a lot of other considerations.) It would be interesting, though, to hear clear halachic reasons that "affectionate" touch (such as a hug) is also prohibited, which I assume it is.

Answer

Saifer chasidim 1090

A Jewish man can not slap hands with a non Jewish woman

And a Jewish woman can not slap hands with a non Jewish man

Even when the hand is coverd with clothing

(The commentaries explain that if they are both Jewish it is OK when the hand is covered with clothing (but only if it is not done for the man to be able to see the woman for a longer time))