Dander consists of small scales or flakes of dead skin cells that are continually shed by all animals. Light and sticky, dander is easily transported by air currents and often becomes attached to objects or people. In the household, dander is a common element of house dust, particularly in homes where cats or dogs are present.

The proteins in dander can trigger allergic reactions in sensitive people, causing symptoms such as sneezing, itchy and watery eyes, coughing, wheezing and difficulty breathing. In rare cases, an allergic reaction may progress to a severe and potentially deadly allergic reaction known as anaphylactic shock.

Dander can also trigger asthma attacks in people with allergic asthma, a condition in which the airways become blocked or narrowed causing shortness of breath or difficulty breathing because of an allergic reaction.

All furred and feathered animals shed dander, regardless of hair length or type. Because household pets are the animals most commonly in contact with people, their dander is more commonly associated with allergies. According to the American Academy of Allergy, Asthma and Immunology (AAAAI) nearly 10 million pet owners are allergic to their animals.