Allergens Widespread in Largest Study of U.S. Homes

Allergens are widespread, but highly variable in U.S. homes, according to the nation’s largest indoor allergen study to date. Researchers from NIH report that more than 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 were published Nov. 30 in the Journal of Allergy and Clinical Immunology.

“Elevated allergen levels can exacerbate symptoms in people who suffer from asthma and allergies, so it is crucial to understand the factors that contribute,” said Dr. Darryl Zeldin, senior author and scientific director at NIEHS.

Using data from the 2005-2006 National Health and Nutrition Examination Survey, the researchers studied levels of 8 common allergens—cat, dog, cockroach, mouse, rat, mold and 2 types of dust mite allergens—in the bedrooms of nearly 7,000 U.S. homes.

They found that the presence of pets and pests had a major influence on high levels of indoor allergens. Housing characteristics also mattered—elevated exposure to multiple allergens was more likely in mobile homes, older homes, rental homes and homes in rural areas.

For individual allergens, exposure levels varied greatly with age, sex, race, ethnicity and socioeconomic status.

Differences were also found between geographic locations and climatic conditions. For example, elevated dust mite allergen levels were more common in the South and Northeast and in regions with a humid climate. Levels of cat and dust mite allergens were also found to be higher in rural areas than in urban settings.