Why such bad reactions to mustard/vinegar

Of all the nasty chemicals out there and heavt metal laden foods, it makes no sense to me that regular mustard destroys my intestines.

It's my fault because I know get this reaction, but sometimes I can't resist it.

Does anyone have a clue why mustard or vinegar would cause such severe stomach symptoms? I say vinegar because it is the first ingredient in mustard and I'm not sure which ingredient is causing the problem. I know some vinegars have gluten in them but I can eat a fair amount of gluten with not too manh problems.