The term "dander" refers to the small dead skin cells continually shed by animals. All furred and feathered animals shed dander, including cats, dogs, hamsters, guinea pigs, ferrets and birds. Dander itself is very light, sticky and easily airborne. Riding on air currents, dander can stay airborne for hours until it settles on a surface, where it can remain for months.

Because dander is so easily transported and tends to stick around, it can (and does) enter areas where animals do not reside. Researchers have documented comparatively high levels of dander in office buildings and homes that do not have pets.

Dander triggers an allergy when the flakes are inhaled into the respiratory system, come into contact with the eyes or get lodged inside the mucous membranes that line the nasal passages. Although the saliva, urine and blood of animals can also trigger allergic reactions in sensitive people, dander is the most common cause of animal allergies.

In contained areas, such as a home, the accumulation of dander is likely to trigger an allergic reaction in people with dander allergies. Animal dander is commonly found in household dust. By contacting clothes or other material outside, dander can be easily transferred into the house.

Although all furred and feathered animals that have skin produce dander, there are differences in the amount produced. For example, young animals tend to shed less and therefore produce less dander. The amount of dander can also depend on the size of the animal. A smaller animal will produce less dander than a larger one, for instance. Recent research has also suggested that the color of an animal’s fur may play a role in the severity of a patient’s symptoms. According to the study, exposure to dark cat hair resulted in a greater amount of symptoms. However, more research is needed.

Furthermore, some dogs shed their skin more quickly than others. Cocker spaniels, German shepherds and Irish setters shed their skin more frequently than poodles and schnauzers. Dog breeds that shed their skin less frequently generally produce less dander.

Dander is specific to particular animal species because the cells and proteins in dander vary. Dog dander is different than cat or bird dander, for example. As a result, people with allergies to dog dander may not be allergic to cat dander. However, some people have allergies to both dogs and cats, because they are allergic to the particular cells and proteins in both types of dander.  

Because all animals have skin, there is no such thing as a hypoallergenic animal. Sensitive people may have an allergic reaction to any animal regardless of hair length or type, size or breed. All of the following animals have dander that can potentially trigger an allergy (Note: This is not a complete list):