
Hi Karen,
unfortunately ANY ingredient can either alone or in a combination cause ear and other problems if the dog is allergic or intolerant to any ingredient being fed to it.
The most common intolerances are beef, chicken, dairy, gluten (any form), wheat, corn/maize. If you want to start looking towards a change of diet then it would be better to find either a complete with minimal *novel* ingredients such as Wafcol Salmon & Potato or prepare a novel ingredient based home diet whether cooked, part cooked or raw.
HTH, best wishes,
Teri :)