Allergy is defined as a "harmful, increased susceptibility to a
specific substance," also known as hypersensitivity, while immunity
is characterized as a "protective, enhanced resistance."
Indoor allergens play a major role in allergic diseases such as asthma
and perennial allergic rhinitis. Most Americans spend more than 20 hours
indoors each day.
Outdoor allergens (pollens) play a major role in seasonal allergy
symptoms.
People are exposed to allergens through inhalation, ingestion, contact
with skin and injection.
Viral upper respiratory infections can aggravate allergies.
Statistics:
Estimates from a skin test survey suggest that allergies affect as
many as 40 to 50 million people in the United States.
Allergic diseases affect more than 20% of the U.S. population.
Allergic diseases are the sixth leading cause of chronic disease in
the United States.
It is estimated that in 1998, increased absenteeism and reduced productivity
due to allergies cost U.S. companies more than $250 million.
New Research:
Dog and cat allergen is found in all homes in the United States (JACI
July 2004; Samuel J. Arbes, Jr. DDS, MPH, PhD, et al).
Allergen avoidance using school clothing or banning of pets reduces
airborne cat allergen in classrooms (JACI June 2004; Karlsson, et al).