It may contain fibers from various fabrics, cotton lint, feathers, and other stuffing material. Dust often contains microscopic mites, which live in bedding, furniture, and carpets. The dust particles that are often visible floating in a stream of sunlight, are dead dust mites and their waste products. It is the waste products of these mites that stimulates the allergic reaction. Household pets are the main cause of allergic reactions to animals.
Cats are the number one culprit.
It is now known that pet allergy is caused by the proteins present in animal saliva and not by their fur. Animals can however carry the allergen on their dander, especially cats who like to clean their skin. Guinea pigs and gerbils are more popular these days as pets, and they can also cause allergic reactions in some people. Allergy to pets may take years to develop and the symptoms may persist for some time even after the contact with the pet has ceased. Additionally, allergens from pets can stay in a home for months after the pet is removed.