"These data confirm that cockroach allergen is the primary contributor to childhood asthma in inner-city home environments," says Kenneth Olden, PhD, director of the National Institute of Environmental Health Sciences (NIEHS). "However, general cleaning practices, proven extermination techniques and consistent maintenance methods can bring these allergen levels under control."
The study, published in the March 2005 issue of The Journal of Allergy and Clinical Immunology, is the first large-scale study to show marked geographic differences in allergen exposure and sensitivity in inner-city children. Most homes in Northeastern U.S. cities had high levels of cockroach allergen, while those in the South and Northwest had dust mite allergen levels in ranges known to exacerbate asthma symptoms.
Cockroach allergen comes from several sources, such as saliva, fecal material, secretions, and dead insect bodies. People can reduce their exposure to cockroach allergen by eating only in the kitchen and dining room, putting non-refrigerated items in plastic containers or sealable bags, and taking out the garbage every day, according to the researchers. Other measures include repairing leaky faucets, frequent vacuuming of carpeted areas and damp-mopping of hard floors, and regular cleaning of countertops and other surfaces.
"We found that a majority of homes in Chicago, New York City and the Bronx had cockroach allergen levels high enough to trigger asthma symptoms, while a majority of homes in Dallas and Seattle had dust mite allergen levels above the asthma symptom threshold," says Rebecca Gruchalla, MD, associate professor of internal medicine and pediatrics at the University of Texas Southwestern Medical Center and lead author of the study.
"We also discovered that the levels of both of these allergens were influenced by housing type," says Gruchalla. "Cockroach allergen levels were highest in high-rise apartments, while dust mite concentrations were greatest in detached homes."
While cockroach allergen exposure did produce an increase in asthma symptoms, researchers did not find an increase in asthma symptoms as a result of exposure to dust mite and pet dander. "Children who tested positive for, and were exposed to, cockroach allergen experienced a significant increase in the number of days with cough, wheezing, and chest tightness, number of nights with interrupted sleep, number of missed school days, and number of times they had to slow down or discontinue their play activity," says Gruchalla.
While cockroaches are primarily attracted to water sources and food debris, house dust mites, microscopic spider-like creatures that feed on flakes of human skin, reside in bedding, carpets, upholstery, draperies, and other "dust traps." Dust mite allergen proteins come from the digestive tracts of mites and are found in mite feces.
Researchers tested 937 inner-city children with moderate-to-severe asthma symptoms. The children, ages 5 to 11, were given skin tests for sensitivity to cockroach and dust mite allergens, pet dander, and mold. Bedroom dust samples were analyzed for the presence of each allergen type.
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