If I could actually manage to avoid all "no-nos", I still end up with headaches and other symptoms from the seemingly healthy foods that are on my allergenic foods list. Your suggestion is but one of many that I've tried already, and that do not do anything for my obvious symptoms if I can't also avoid all of my allergenic foods.

That's just it - those of us with multiple foods sensitivities have a lot more than just avoiding your suggested item to deal with, and there are times that using that bad item is preferable to eating, say, a big plate of spaghetti that will punish me for days and days afterwards.