Foods as triggers for dog allergies

Grains:

Dogs aren’t biologically built to fully digest grains and over time can lead to Leaky Gut. Leaky Gut is where food molecules leaks into the bloodstream and potentially causes a reaction. 

Dairy:

The protein casein that’s found in milk and dried milk products can cause an allergic reaction in some dogs. Casein also contains lactose which some dogs can be intolerant to. 

Corn:

A substitute for grain, corn is frequently added to processed dog food which can lead to dogs becoming over-exposed to it. Corn is in high sugars which can lead to Leaky Gut allowing food molecules to pass into the bloodstream. 

In reality dogs can be allergic to anything so if you feed them something new and they start to show a reaction they could be allergic to something in it. Intolerances can develop gradually over time
so it is possible that your dog could start reacting to something that they’ve previously had no issues with.

Dog allergy guide.