Hi Megan,
For food allergies, chicken is by far the most common because many dog foods are primarily chicken (a relatively inexpensive protein) or contain at least some chicken–for example, chicken fat as a second ingredient in a version labeled “beef.”
The brands you list are all processed kibble, and even pricier grain-free is basically the same highly processed “food” product recently linked to heart disease.
Many dogs with various health concerns have had luck eating raw food instead, just simple ingredients of meats and various nutritional vegetables and fruits that dogs are biologically geared to eat and thrive on.
You can find some raw varieties in grocery and pet stores, and there are now many online companies that deliver, while we have had luck with a more affordable California company 7 Sky Dog Food.
Our Heeler had a seasonal summer skin rash–common with the breed, that still occurs, but has been greatly diminished. He now doesn’t scratch and lick to the point of creating sores.
Good luck!
