Short answer is that there is apparently a book that lists the ingredients of the food items that is shared between the booths.
Long answer: I have some serious food allergies and some minor ones, including shellfish, salicylates, ginger, turmeric, sulfites, etc. I will admit that the Food & Wine Festival sucked for us because the ingredients of each booth are not listed. We asked a CM at one booth if they knew the ingredients or if there was a book or something that listed them after multiple reactions to things that seemed okay based upon their descriptions. That CM said nothing like that existed so I basically just stopped participating in the festival.
After I returned home and contacted guest services to leave feedback suggesting that they create a book of ingredients for those of us with food allergies, I learned directly from the Special Diets Team that a book does indeed exist. There are apparently a few books shared amongst the booths, so not every booth has one, but they should be able to get one for you to look at. If a CM says that it doesn't exist then they are mistaken and just try to ask a different CM.