Common Household Allergens

Biological contaminants include bacteria, molds, mildew, viruses, animal dander and cat saliva, house dust, mites, cockroaches, and pollen. There are many sources of these pollutants. Pollens originate from plants; viruses are transmitted by people and animals; bacteria are carried by people, animals, and soil and plant debris; and household pets are sources of saliva and animal dander. The protein in urine from rats and mice is a potent allergen. When it dries, it can become airborne. Contaminated central air handling systems can become breeding grounds for mold and other sources of biological contaminants.

Dust mites are the most common indoor allergens. Dust mites are microscopic eight-legged bugs related to spiders and ticks. They live primarily in fabric -- carpets, upholstery, bedding, draperies, stuffed animals -- and prefer warm, moist environments. They live on flaked off human skin. Dust mites can be controlled by frequent vacuuming, covering mattresses, removing stuffed animals and most importantly, by reducing humidity.

Animal allergens are another common cause of asthma. Cats and dogs are the most likely offenders because they are the most common house pets, but any furred animal, including rats and mice, can carry these allergens. It is usually not the animal fur itself that causes a reaction but substances in animal saliva, urine or skin secretions. So a long-haired dog or cat is no more likely than a short-haired one to cause allergic reactions, except that long-haired pets are usually bigger and have larger body surface areas. Cat allergens are quite “sticky”. We recently tested a home that had moderately elevated levels of cat allergen, even though a cat hat not been present in the home for over 5 years.

Cockroaches are another common indoor allergen and a particular problem in cities and in warmer climates

Molds grow indoors and out, and many molds are known allergens.