Great, I got long, complicated answers (as in - too much for this brain to remember and type out accurately) to both questions, so will email them to you once I get them.
Traci, the vets said the reaction to the wet food sounds like a food allergy, and nothing to do with whether the food is wet or dry ... again, a long answer, but I'll email you the file.
As for the chewing of cardboard, they talked about it maybe being a soothing thing to do, like some people chew gum ... you'll hear it!
Any questions for this week's Ask the Vets? It will be Thursday afternoon at 2 Eastern, so questions before then would be good!
This week will have Dr. Kanfer - a long-time experienced veterinarian from Florida, and Dr. Cathy from the midwest who has plenty of horse and livestock experience, and is very into nutrition issues with pets.