Over 90 percent of homes had three or more detectable allergens.  Allergens are widespread, but highly variable in U.S. homes, according to the nation’s largest indoor allergen study to date. Researchers from the National Institutes of Health report that over 90 percent of homes had three or more detectable allergens, and 73 percent of homes had at least one allergen at elevated levels. The findings(link is external) were published November 30 in the Journal of Allergy and Clinical Immunology.