More than 50 percent of the current asthma cases in the U.S. are the result of allergies, especially to cats, according to a new National Institutues of Health (NIH) study.
Asthmatics, people with allergies and doctors alike have long debated possible connections between pets, dust, ragweed, mold, fungus, foods, cockroaches, traffic exhaust, smog, pollen, trees blooming, leaves falling … and wheezing attacks, which can be terrifying and life-threatening.
The lack of consensus can be maddening for those who stay up at night with kids gasping for breath, wondering what can be done. Some parents have wondered if children diagnosed with asthma, and medicated for the condition, don't actually have an untreated allergy instead.
The new research shows that 56.3 percent of asthma cases can be attributed to atopy, or allergies, which result from gene-environment interactions and can be measured by a positive skin test to substances in the environment, said Darryl C. Zeldin, a senior investigator at the National Institute of Environmental Health Sciences, part of the NIH.
Cat allergens were found to account for 29.3 percent of the asthma cases, followed by the fungus Alternaria at 21.1 percent and White Oak at 20.9 percent. White Oaks are long-lived trees native to eastern North America and found as far west as Texas and Minnesota.
"This study tells us that allergy is a major factor in asthma," said Peter Gergen of the National Institute of Allergy and Infectious Diseases (also part of NIH), lead author of the study available online today in the Journal of Allergy and Clinical Immunology. "But this study also tells us that thee are many people who get asthma who don't have allergies. We need to do more research to understand what is causing the asthma that is not related to allergies."
Other allergens were tested, such as ragweed, dustmites, Russian thistle, Bermuda grass, peanuts, perennial rye and german cockroach, but only cats, the fungus and white oak were positively and independently associated with asthma.
"Sensitization to cat appears to be a strong risk factor for asthma in this study," Zeldin said. Some research suggests that exposure to cats early in life may protect children from allergies, but if children have cat allergies or get asthma-like symptoms, parents should consult their physician about whether to get rid of pets.
About 10,500 individuals were tested for their link to atopy, or allergies, as part of the Third National Health and Nutrition Examination Study, a national representative sample of the U.S. population.
"This study confirms that the environment plays a major role in the development of asthma," Zeldin said. "Given the complexity of this disease it won't be easy, but if we can prevent or reverse atopy, we could reduce a large proportion of asthma cases."
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Robin Lloyd was a senior editor at Space.com and Live Science from 2007 to 2009. She holds a B.A. degree in sociology from Smith College and a Ph.D. and M.A. degree in sociology from the University of California at Santa Barbara. She is currently a freelance science writer based in New York City and a contributing editor at Scientific American, as well as an adjunct professor at New York University's Science, Health and Environmental Reporting Program.