Scientists at the National Institute of Environmental Health Science (NIEHS), one of the National Institutes of Health (NIH), have found that detectable levels of mouse allergen exist in the majority of United States of America homes. NIEHS researchers analyzed dust samples, asked questions, and examined homes in the first National analysis of Lead and Allergens in Housing, a analysis of 831 homes. Allergen levels were studied and related to demographic factors and household characteristics.

82% of United States of America homes were found to have mouse allergens. The findings by Cohn et al. appear in the June 2004 issue of the Journal of Allergy and Clinical Immunology.

The analysis was conducted using established sampling techniques to ensure that the survayed homes were representative of United States of America homes. The homes were sampled from seventy-five randomly selected areas (usually counties or groups of counties) across the entire country. The 831 homes included all regions of the country (northeast, southeast, midwest, southwest, northwest), all housing types, and all settings (urban, suburban, rural).

The selection of homes was controlled to be a representative sample of United States of America homes. For statistics derived from the 831 homes, the contribution from each home was weighted as necessary to ensure that the statistics are representative of the United States of America population.

Dust samples used in the study were collected from kitchen and living room floors, upholstered furniture, beds, and bedroom floors. Kitchen floor concentrations exceed 1.6 micrograms of allergens per gram of dust in about one in five homes (22%). The amount of these allergy-triggering particles on the kitchen floor is high enough to be associated with allergies and asthma. Residents of high-rise apartments and mobile homes are at greatest risk, but the allergen is also present in all types of homes.

The NIEHS study, with collaborators at Constella Group, Inc. and the Harvard School of Public Health, characterized mouse allergen prevalence in a representative sample of United States of America homes and assessed risk factors for elevated concentrations. The odds of having elevated concentrations were increased when rodent or cockroach problems were reported.

Exposure to mouse allergen is a known cause of asthma in work-related settings. Until now, exposure to these allergens had not previously been studied in residential environments on a national scale. Clinicians should consider these risk factors when treating allergy and asthma patients.