The study was conducted by researchers led by Darryl C. Zeldin, M.D., a senior investigator at the National Institute of Environmental Health Sciences and Peter Gergen, M.D., M.P.H, of NIAID's Division of Allergy, Immunology and Transplantation.
They found that more than 50 percent asthma cases were attributed to allergies, out of which 30 per cent cases were attributed to cat allergy.
Dr Zeldin said that the new research showed that 56.3 per cent of asthma cases attributed to atopy, a condition that resulted from gene-environment interactions and can be measured by a positive skin test to allergens. "It has long been debated whether people who develop asthma have a genetic propensity to develop allergies, or atopy. This new research shows that 56.3 percent of asthma cases are attributed to atopy."
Zeldin and his team pointed out that from the study it was found that cat allergy was one of the major causes for asthma, however, some studies show that exposure to cats, particularly early in life, may be a protective factor against asthma.
"Sensitization to cat appears to be a strong risk factor for asthma in this study. We are not advocating parents get rid of pets, but if you suspect that you or your child might have cat allergies or get asthmatic-like symptoms, you should consult with a physician about the best course of action for your family," Zeldin said.
The researchers examined approximately 10,500 individuals for the skin test data for ten allergens or allergy causing substances in the environment. 29.3 per cent of the asthma cases accounted to a positive skin test reaction to cat allergens, which was followed by the fungus Alternaria at 21.1 percent and white oak at 20.9 percent. During these tests, skin was exposed to allergens and the size of the reaction on the skin determined a positive test.
"Each of 10 allergen-specific skin tests was strongly associated with asthma; however, after adjustment by a variety of subject characteristics and all the allergens, only skin tests to cat, Alternaria and white oak were independently and positively associated with asthma," Peter Gergen said. Other allergens tested included: Ragweed, dust mites, Russian thistle, Bermuda grass, peanuts, perennial rye and German cockroach.
"This study tells us that allergy is a major factor in asthma. But this study also tells us is that there 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," Gergen said.
Zeldin concluded that the study confirmed that the environment played a major role in the development of asthma. "Given the complexity of this disease it won't be easy, but if we can prevent, block or reverse atopy, we could reduce a large proportion of asthma cases," Zeldin said.
The study is issued in the Journal of Allergy and Clinical Immunology.