Allergens are substances which in some people trigger the hypersensitive state of allergy and propel the formation of reaginic antibodies. Allergens may be naturally occurring or of synthetic origin and include pollen, mold spores, dust, animal dander, insect debris, foods, blood serum, and drugs. Identification of allergens is made by studying both the site of symptoms (for example: inhalants such as molds, pollens, and dander usually affect the eyes, nose, and bronchi while cosmetics often affect facial skin and hands) and the time that symptoms appear (for example: seasonal allergy to pollen).
Most people with perennial allergies such as asthma, hay fever or other outdoor allergies think of their home as a haven where they can escape their allergies. Contrary to this belief, houses and apartment buildings accommodate their own allergens. The inside of your home actually traps allergens, making them impossible to avoid.
Although many allergens in your environment can trigger allergic symptoms, house dust is the main culprit in indoor allergies. House dust is an airborne mixture that might contain fine particles of soil and plant material from indoors or outdoors, particles of human and animal skin (dander) and hair, fabric fibers, mold spores, dust mites, fragments of insects that have died and their waste, food particles, and other debris.