Some dog beds have dust mite covers, and this can help reduce dust allergies. Dust mites are microscopic (up to 0.3 mm) spider-like creatures that feed on flakes of human skin and reside in bedding, carpets, upholstery, draperies and other "dust traps."
The number of dust mites in a home depends on its cleanliness, but also on the amount of moisture in the house; dry houses in very cold climates or on high mountains have few mites, but houses in temperate climates and normal altitudes have more.
Dust mite droppings contain left-over enzymes which the mites use to digest the skin flakes. Dust mite droppings are believed to be the most important single cause of asthma worldwide.