I think there is some relationship between allergens and crohns/IBD. I don't know what it is for sure yet, but it is part of what has me consistently skeptical about my allergy injections. I worry that since allergies arouse the immune system and get it worked up to fight, that it may be possible that it restarts the auto-immune crohns attack. Sadly, my GI told me to talk to my ENT about this. The ENT said it is fine, but I worry that he would say that no matter what so long as I am walking and breathing....the injections are big money. I feel that my GI should have knowledge about this. I don't know. I suppose this isn't a great response. Sorry. Anyway, I am on Allegra, and haven't noticed anything, but I have the constant exacerbation of allergy injections too.