Allergens: Pollen Pollen is the most common cause of seasonal allergic rhinitis, sometimes known as "hay fever." Allergens: Animals Household pets, like cats and dogs, are the most common sources of animal allergens. Allergens: Dust and Dust Mites Dust mites are microscopic organisms that can live and thrive throughout homes and businesses. Your Child's Allergies: Dust Mites Detailed information on dust mite allergens On the Air: Which Products Help You Breathe Better? Here are some helpful tips for understanding the air in your house and the air-quality appliances that can alter it. Asthma: When to Get an Allergy Test If you think you may have allergies, talk with your health care provider about getting tested.