It's a really bad idea to get irrational or emotional aversions to any particular food because that only means you choose other things to eat that may be no better. Obviously if you react badly to any product you stop using it, in the case of sweetener most manufactured products use that or sugar, the only way you are going to avoid that is to make all your own food from the basic ingredients.
I'm lucky I don't have food alergies but I do cook with mostly basics, it's no big deal, I get organized a make the effort on most Sunday mornings cooking lunch and baking at the same time. Leftovers go into a curry or pasta mid week (no bought sauces), round off the week with salads in summer, casseroles in winter or fish.
Basics in any supermarket or farm shop if you are lucky, enable most unnatural ingredients to be avoided, if either of us had an allergy I certainly would not rely others, buying sandwiches from Pret a Manger or Subway pretty much guarantees that the staff won't have a clue what's in it..