Joel Griffies, DVM:
There's an awful lot of misinformation and misconception about food allergy in dogs. The most common triggers for food allergy really include the most common ingredients in the foods that our dogs and cats eat. So from ingesting a particular set of ingredients, whether chicken or corn or fish or beef, they can become more and more sensitive to those ingredients, which means the more that they eat them, the more they cause a reaction. They can cause itchiness, licking, scratching, chewing, a variety of secondary infections. But the thing to realize is that food allergy is clinically indistinguishable from atopic dermatitis or environmental allergy. And so as we go through the investigative process, we have to evaluate these different components in order to understand which one plays the most significant role.
The only reliable way to diagnose food allergy, at this point, is by doing a strict elimination diet trial. It's important for us to remove all ingredients that an animal might have ingested, because any one of them can be causing a lot of our problems. While we all would love to have a very quick answer, elimination diet trials often take six to eight weeks, or maybe even 10 to 12 weeks. It may take that long for the effects of the previous ingredients to be eliminated from their system. Because of the complexities of investigating and identifying food allergies, it's often worthwhile for a pet owner to consider consulting a veterinary dermatologist who is accustomed to identifying these cases on a day-to-day basis. This often allows a pet owner to arrive at a solution in a much quicker fashion, and come up with a plan that potentially works for a lifetime.