Cockroach allergen is the primary contributor to childhood asthma in inner-city homes

New results from a nationwide study on factors that affect asthma in inner-city children show that cockroach allergen appears to worsen asthma symptoms more than either dust mite or pet allergens.

This research, funded by the National Institute of Environmental Health Sciences (NIEHS) and the National Institute of Allergy and Infectious Diseases (NIAID), is the first large-scale study to show marked geographic differences in allergen exposure and sensitivity in inner-city children. Most homes in northeastern cities had high levels of cockroach allergens, while those in the south and northwest had dust mite allergen levels in ranges known to exacerbate asthma symptoms.

The study results are published in the March issue of the Journal of Allergy and Clinical Immunology.

"These data confirm that cockroach allergen is the primary contributor to childhood asthma in inner-city home environments," said NIEHS Director Kenneth Olden, Ph.D. "However, general cleaning practices, proven extermination techniques and consistent maintenance methods can bring these allergen levels under control."

Cockroach allergens come from several sources such as saliva, fecal material, secretions, cast skins, and dead 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 on a daily basis. Other measures include repairing leaky faucets, frequent vacuuming of carpeted areas and damp-mopping of hard floors, and regular cleaning of counter tops and other surfaces.

NIH provided $7.5 million to researchers at the University of Texas Southwestern Medical Center at Dallas and seven other research institutions, including the Data Coordinating Center at Rho, Inc., for the three-year study.

"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," said Dr. Rebecca Gruchalla, 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," noted 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," said 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 allergens are proteins that 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.

This study was part of the larger Inner-City Asthma Study, a cooperative multi-center project comprised of seven asthma study centers across the country. The goal of the study was to develop and implement a comprehensive, cost-effective intervention program aimed at reducing asthma incidence among children living in low socioeconomic areas.