Allergy to cats is tremendously common. It is occurring in up to 25 percent of people with allergies. Cat allergy is more common than allergy to dog dander, which may be related to the potency of cat hair and dander as an allergen as well as the fact that cats do not bath frequently.
The primary cat allergen, called Fel d 1, is found in cat saliva, dander from sebaceous glands in the skin, fur, and anal sebaceous glands. Other cat allergens, including albumin, are found in the urine, saliva and blood.
Cat allergen is produced in massive volume, particularly by castrated male cats as the allergen is partially under hormonal control. The dander is constantly airborne, sticky, and found in public places, even where there are no cats. This is due to the dander being carried on the clothing of people who have cats, then shed in public places. Therefore, cat allergen is a component of house dust, even in homes where there is no cat. This makes cat allergy a serious problem.
The size of the cat dander particles is extremely small, and is inhaled deep into the lungs. Cat dander is therefore a common cause of allergic asthma, and cat owners who are allergic to cats are more prone to the development of asthma symptoms.