Dander is minute scales that fall from the hair, feather, and skin of all warm-blooded animals.
Animal dander carries antigens that can cause allergic reactions in sensitive people.
House dust mites are microscopic insects that are related to spiders. The fecal material from dust mites is partially composed of substances to which some people are allergic. Constant exposure to these allergens may result in a state of chronic inflammation that may put you at greater risk for acute asthma flare-ups or nasal symptoms. Cats tend to be more allergenic than dogs for most allergic people, although some people are more sensitive to dogs than cats. Non-allergenic breeds of dogs or cats do not exist.