My pixiebob developed food allergies last year. His symptoms were itchy face and neck. He would scratch so badly that he would rip out the fur and it looked like ringworm. He was tested for all known parasites and we were given meds to sooth his skin. At the time, he was only eating beef and chicken so it was fairly easy to diagnose - we removed the beef and he had another reaction about a month later so we switched him completely to beef and removed the chicken. The tricky part is that they add chicken to everything. I was feeding homemade raw so the food part was straightforward but chicken flavor was added to supplements (Mazuri) and medications (Liquid Hepato). Bring a magnifying glass and read the entire list of ingredients to make sure there's no chicken in anything he consumes. Once the allergy develops, it worsens rapidly over time and the smallest exposure will cause a severe reaction. As a result of this experience, my cats now eat rabbit, turkey, beef, quail, lamb, pheasant and venison.