Allergens Widespread in Most U.S.Homes.

• Position: YOUR LIFE

Allergens are widespread, but highly variable in U.S. homes, according to the nation's largest indoor study to date. Researchers from the National Institutes of Health, Bethesda, Md., report that more than 90% of homes have three or more detectable allergens, and 73% have at least one allergen at elevated levels. The findings were published 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," says senior author Darryl Zeldin, scientific director at the National Institute of Environmental Health Sciences, which is part of NIH.

The researchers studied levels of eight common allergens--cat, dog, cockroach, mouse, rat, mold, and two types of dust mite--in the bedrooms of U.S. homes. They found that the presence of pets and pests has a major influence on high levels of indoor allergens. Housing characteristics also mattered--elevated exposure to multiple allergens is more likely in mobile, older, rental, and rural homes.

For individual allergens, exposure levels vary greatly based on age, sex, race, ethnicity, and socioeconomic status. Differences also are found between...