Food allergies in dogs generally develop when a dog is overexposed to certain ingredients. Because most dogs eat the same brand and kind of dog food and treats for years on end, this can be a common occurrence.
Ingredients like beef, corn, wheat and dairy are commonly used in most dog foods and treats. Because of this, many dogs can no longer process these ingredients. Even worse, developing an allergy to one ingredient can lead to a "chain reaction" of sorts...causing a dog to develop allergies to other ingredients.
Some of the symptoms of food allergies in dogs are ear infections, hot spots, dry or itchy skin, and even digestive issues.