Well, how about 3 weeks just to see if it makes a difference? People here have gone on an anti-candida diet for a few months. If we can do it, you can do it. Really, 3 weeks is a not a long time. If the diet does not help, you can go back to your favorite foods after 3 weeks.
If you have a nickel allergy, eating foods high in nickel will keep causing an allergic reaction...most likely affecting the lips since it did with someone else with a nickel allergy. When someone stops exposure to allergen causing peeling lips, the lips heal. In other words, an allergic reaction does not permanently damage your lips. Personally, if nickel was causing my EC I would go on the strict diet. I would rather not be on a gluten-free diet myself, but you do what you have to do.
Don't forget to avoid multivitamin for 3 weeks since it also has nickel in it. Also, run water a few seconds before you fill the glass.