Allergies in dogs are much like allergies in humans. They have both genetic and environmental causes. While you can't change the genetics of your dog, environmental factors are commonly: pollen, dander, plants, insects, foods and food additives such as corn, rice and wheat. Allergies can cause symptoms such as excessive itching, scratching, and grooming; rashes; sneezing; watery eyes; paw chewing; and skin inflammation. In some cases, dogs have conditions, such as atopic dermatitis, that is associated with and may be caused by allergies.