Food allergies in dogs and cats can manifest in disease of the gastrintestinal tract, skin and ears, and respiratory systems.  Dr. Roger and Dr. Karen discuss how a hypoallergenic food trial is correctly implemented, why they commonly fail, and why food trials are a common sourse of frustration for pet owners and veterinarians alike.  For more content from Dr. Roger Welton and Dr. Karen Louis, visit their respective blogs at Web-DVM.Net and VetChick.com.  E-mail comments for our co-hosts to address on the air to comments@web-dvm.net.