I am not a very allergic person. BUT I do get one weird allergy which only occurs on my hands and elbows. So I may be the only one here, but I think it is possible that one may be allergic to someone only on some parts of thew body.
At the same time, as many have written, there may be subtle differences in your process, involving soap etc., which may be the source of your issue.
You may want to read these two thread resources on FUD, which are very similar to each other, although not exactly the same: