Animal allergens play a significant role in the pathogenesis of asthma and allergic rhinitis, and are potent causes of acute and chronic symptoms. Although cat and dog allergens are the most important, exposure to a wide variety of other furred animals is not uncommon. Recent reports state that 60% to 70% of households in the western world have at least one pet. Because of this significant exposure, hypersensitivity to animals has become increasingly important. This review focuses on the importance of animal allergens, concentrating on cat and dog allergens, but including others as well. It also discusses the pathogenesis, diagnosis, prevention, and management of animal allergy.