Diet can absolutely cause eye staining, but its important to remember that the breed of the dog can have just as great of an effect as well. Dogs with bulging eyes, like many chihuahuas for example, routinely have eye staining regardless of diet.
Eye stains are usually a sign of some sort of food intolerance or allergy. I have a dog in particular who gets massive staining when eating a pea-heavy food, which many grain free kibbles qualify as. This dog gets no eye staining when eating a food who’s carbs are majority grain or majority potato based.
But, I also have two chihuahuas who had massive staining while on puppy chow in their foster home and now have some, but not much, eye staining with quality foods (honest kitchen, acana, etc). I credit whats left of their eye staining to their breed and their bulging eyes.
So anyways, if your dog did not have much staining before but has massive staining now then consider switching foods. Also, you can do even better by stocking five or so foods at your home and switching every meal. That way your dog’s body will not develop new allergies and will not be lacking in any nutrients or minerals that any one food may be lacking in.
