I thought erythritol was derived from fruit - mostly pears, melons, grape. Just looked into it and see some mushrooms, and some fermented foods are included in the list. Are you sure it can be extracted from corn?
I went to a lecture on natural sweeteners at one of th e trade shows a few years ago and they said commercial erythritol was from corn.
Also, interesting that FOS is a potential flow agent. Why would it (or the erythritol) cause a reaction?
Theoretically they should not cause any problems. But there are always going to be people that will have that rare reaction, just like the rare condition of being allergic to the sun. Or the girl in England allergic to her own tears.