In the first study to examine levels of airborne mouse allergen in inner-city homes and to associate those levels with dust levels of the allergen, researchers found that mouse allergen levels are often comparable with those levels seen in animal facilities.

Noting that the number of homes with detectable mouse allergen surprised the researchers, lead author Elizabeth Matsui, MD, said that in many instances the allergen had reached levels that would cause asthma symptoms in sensitized adults.

The researchers based their findings on allergen skin testing and home inspection for 100 inner-city children with asthma. Indicators of detectable airborne mouse allergens included cracks in doors or walls, food remains in the kitchen, and mouse infestation.

The results of the study showed that dust samples from all the bedrooms tested positive for mouse allergen. Allergen levels that are >0.1 ng per m³ fall within the range found in animal facilities and may trigger asthma symptoms. The researchers found those levels in about a quarter of the homes.

"The message for clinicians is to test for allergic sensitization to mice in kids with asthma, especially those living in the inner city,"concluded Dr. Matsui. (The findings were reported in the Journal of Allergy and Clinical Immunology, February 2005.)