What are facts about the allergies animals can have and how to treat them?

Focusing on dogs, there are three major allergen groups that are frequently seen: parasite allergy (flea, tick, etc), food allergy (beef, chicken, rice, etc.) and environmental (grass, pollen, dust mite, etc.). The most common sign of Allergies in dogs is recurrent skin and ear infections due to excessive scratching. Treatment for allergies in dogs include aggressive parasite control (such as year-round topical flea/tick preventative), diet modification (for instance, to a novel protein diet like duck or salmon) and allergy shots similar to what humans can receive.

Cats do not appear to be as affected by allergies as dogs.