Primary versus secondary food allergies
The main food allergens are the gluten grains (WHEAT, barley, and rye), dairy products, soy and corn. These are what I call the "big 4"...the four foods that can do damage to the intestinal villi, during which process the food allergies are formed. This is known fact.
What is also known fact is that once the damage is done and the natural barriers of the intestine are disrupted, ANY foods (proteins) passing through that damaged area are subject to the allergic response. That is why celiacs (gluten intolerants) like myself are notorious for having multiple food allergies. Some are allergic to 20, 30 and even 50 foods and commonly allergic to foods that are otherwise healthy for us.
This is where the uniform nature of commerical diets becomes a real problem. If a food contains wheat, corn, lamb and rice (like sooooo many puppy chows and adult foods do now), then you can see what happens...the wheat and corn damage the gutin sensitized individuals and the immune system then latches onto the lamb and rice. As a result of this all-too-common scenario, I see LOTS and LOTS of lamb and rice alllergies.
The starting point for the treatment of ALL allergy sufferers is the elimination of all of the "big 4". Most do well once that is accomplished. If not, then the fastest way to an answer is food allergy testing ( I use VARL in California) to determine the secondary food allergies that the individual has developed. Other than that, it is pretty much guess work.
A great alternative is the use fo potato-based foods with novel protein, such duck, venison, or rabbit and potato. I prefer the IVD line at this point as they are made in a dedicated facility where they only make these foods, minimizing cross contamination.
Hope this helps,
John