I don't think the underline cause for my EC is allergy. MY lips almost never burn/itch and they aren't swollen, only peeling and dry.
My doctor told me that if the cause was allergy the steroid cream would have helped(in my case it didn't have any effect).
I have also tried the elimination diet, changing shampoo/ toothpaste and all that stuff, so I really don't see how allergies have anything to do with it.