July 8, 2004 -- It not only rains like cats and dogs outside your home, but allergy-causing traces of cats and dogs are most likely inside your home too, according to a new report.
Researchers found cat and dog allergens or dander were present in 100% of homes screened in the first national survey of allergens in housing. Allergens are substances that may cause an allergic response in a person.
The survey showed that although a dog or cat lived in only about half of the homes, dog and cat allergens were found in 100% and 99.9% of all the homes, respectively.
"The universality of these allergens is remarkable when one considers that most U.S. households have neither an indoor dog or cat," write researcher Samuel J. Arbes, DDS, MPH, PhD, of the National Institutes of Health, and colleagues.
Researchers say the study shows that pet allergens are easily transported from place to place and may make total elimination of the allergy-causing substances difficult.
Dogs and Cats Are Everywhere
The study, published in the July issue of the Journal of Allergy & Clinical Immunology, used information collected by the first National Survey of Lead and Allergens in Housing. The survey was conducted from 1998 to 1999 by the National Institute of Environmental Health Sciences and the U.S. Department of Housing and Urban Development.
The survey included 831 housing units in a total of 75 locations throughout the U.S. Residents of the homes were asked about pets living in the home, and vacuum-collected dust samples were taken from the bed, bedroom floor, living room floor, and living room sofa.
Researchers analyzed the samples and found average concentrations of dog and cat allergens were about 5 µg/g. Concentrations of pet allergens in homes with cats or dogs were much higher at about 69 µg/g for dog allergen and 200 µg/g for cat allergens, compared with only about 1 µg/g for either allergen in homes without indoor pets.
Researchers say exposures to as low as 1 or 2 µg/g of cat and dog allergens can increase the risk of persons becoming sensitive to the allergen. But higher levels of exposure, such as 8 to 10 µg/g) needed to cause asthma among people with allergies.
The highest concentrations of dog and cat allergens were found on the living room sofa.
In homes with pets, researchers say the higher levels may reflect where the animal likes to spend time. But in homes without pets, it may be the place most likely to come in contact with clothing worn outside the home.
Researchers say dog and cat dander and allergens are easily transported on clothing, which may explain the why pet dander was found in homes without pets. Another explanation may be that pets lived in the home previously and the allergens persisted over time.