Study shows asthmatics more irritated by airborne dog allergens than cat allergens
Man's best friend may be poor company for asthmatics.
Although it's known that people with asthma also tend to suffer with allergies, a new study by the Asthma Clinical Research Network (ACRN) put cats, dogs, cockroaches, and nine other allergens to the test to see how each affected people with asthma.
"Although a greater number of people had reactions to cat allergen, dogs came out on top as promoting greater disturbances in pulmonary function measurements for asthmatics," said Tim Craig, D.O., professor of medicine and pediatrics, Penn State College of Medicine, Penn State Milton S. Hershey Medical Center, and lead author for the study. "This may be surprising to many because it dispels the myth that cats cause more severe allergic reactions."
The study, presented today (May 20, 2003) at the American Thoracic Society International Conference in Seattle, included 809 adults – 361 males and 448 females – from the six medical centers that are members of the ACRN clinical team. Penn State Milton S. Hershey Medical Center is the data coordinating center for the ACRN.
The study assessed skin testing that was done on all patients to determine their specific sensitivities and compared it to tests used to determine asthma stability. The baseline sensitivity test, a skin test, showed that in addition to their asthma, 95 percent of those in the study were allergic to at least one allergen, with the average number of positive tests being five per patient.
Results showed that dogs caused a reaction in 38 percent of patients in the study. About 72 percent of patients were allergic to cats and about 58 percent were allergic to mites. Ragweed grass mix, tree mix, mold and weed mix caused a reaction in 53 percent, 52 percent, 45 percent, 45 percent and 41 percent of patients, respectively. Cockroach, Aspergillus (a mold) and cladosporium (a mold) caused a reaction in 37 percent, 22 percent and 19 percent, respectively.
Researchers took three measurements of the asthmatic reaction to the allergens: amount of air exhaled; amount of nitric oxide in the exhalation; and the make up of the cells of any mucus that may have been coughed up. A reaction would constitute any or a combination of the following: a lower amount of air exhaled from the lungs caused by inflammation, more nitric oxide released from the cells in the respiratory tract and subsequently exhaled due to inflammation, and a specific type of cell called eosinophils, found in phlegm.
"Even though a higher percentage of people had reactions to other allergens, only dog caused a combination of reactions that included less air exhalation and more nitric oxide release due to inflammation, and more eosinophils in the phlegm," Craig said. "For comparison, cats and cockroaches only showed changes in air exhalation. The other allergens were associated with less significant reactions."
Overall, the indoor airborne allergens like cat, dog, cockroach, mold and mite, were associated with more markers of asthma instability than outdoor allergens like tree, weed and grass.
"This study shows that we, as clinicians, should be as diligent as we can in convincing people that they should consider their pets as a possible factor when trying to control their asthma," Craig said.
The ACRN and its studies are supported by the National Heart, Lung and Blood Institute of the National Institutes of Health. This study was approved by the Institutional Review Board (IRB) under FDA regulations at Penn State College of Medicine and by IRBs at each of the clinical centers.
The ACRN clinical centers are: Brigham and Women's Hospital and Harvard Medical School, Boston; University of California at San Francisco; Harlem Lung Center and Columbia University; National Jewish Medical and Research Center; Thomas Jefferson University, Philadelphia; University of Wisconsin, Madison. Denver
Other investigators on the study were: E. Lehman, R.R. Zimmerman, Department of Health Evaluation Sciences, Penn State College of Medicine, H.A. Boushey, principal investigator, University of California, San Fransico, R.F. Lemanske, principal investigator, University of Wisconsin, Madison, G. Pesola, co-principal investigator, Columbia University, and V.M. Chinchilli, principal investigator of the ACRN Data Coordinating Center, Penn State Milton S. Hershey Medical Center.