If you can, check the ingredients of each, the old and the new formula, to see if there are any different ingredients. (The main ingredient should be the same but there may be flavors, coloring, additives, preservatives that account for your reaction.) Even if you see no difference in the ingredients I would not continue on with the new brand but would switch back to the old just to be on the safe side. Itching in the mouth is definitely an allergic reaction. The same thing happens when give in to my own forbidden passion: almonds. (But I eat them in moderation and always keep allergy medicine nearby.) I just can't resist them indefinitely!