4. What are the common food culprits?
Several studies have shown that some ingredients are more likely to cause food allergies than others are. In order of the most common offenders in dogs:
Dairy products (milk)
As you may have noticed, the most common offenders are the most common ingredients in dog foods. This correlation is not a coincidence. While some proteins might be slightly more antigenic than others, many proteins are similar in form and the incidence of allergic reactions is probably associated with the amount of exposure.
(Foster and Smith)