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Increased Allergen Levels in Homes Linked to Asthma

Researchers at the National Institute of Environmental Health Sciences (NIEHS), University of Iowa (IA, USA), Rho Inc., and the Constella Group suggest that that elevated allergen levels in the home are associated with asthma symptoms in allergic individuals. Data from the National Survey of Lead and Allergens in Housing (NSLAH) was analyzed and factors contributing to elevated allergen levels in homes and its association with the individual's asthma status were examined. The study suggests that asthmatics that have allergies may alleviate symptoms by reducing allergen exposures inside their homes. The team's findings may help millions of Americans who suffer from asthma.

"Indoor allergen exposures are of great importance in relation to asthma because most people spend a majority of their time indoors, especially at home," said Darryl Zeldin, principal investigator in the laboratory of respiratory biology at NIEHS and senior author on the paper.

"Our results highlight the importance of reducing exposure to allergens as a fundamental part of asthma management."

The findings, published online in the March issue of the Journal of Allergy and Clinical Immunology, found that 52% of US households have at least six detectable allergens and 46% have three or more at increased levels. The indoor allergens studied included those from dog, cat, mouse, cockroach, dust mite and the fungus Alternaria.

Several factors were found to contribute to the increased concentrations of allergens, including race, income, type of home and sources of allergens, such as the presence of pets and pests. The study also showed that homes with children were less likely to have high allergen levels. The authors noted that this finding may not be surprising since homes with children may be cleaned more frequently than homes without children. Regular household cleaning is a simple yet effective regimen that helps to reduce the overall exposure burden.

According to lead researcher Paivi Salo of NIEHS, the study provides useful information to asthma patients. "Our results highlight the importance of reducing exposure to allergens as a fundamental part of asthma management," she said. "Although homes cannot be made allergen free, asthmatics that have allergies may need to do a better job in reducing allergen levels in their homes to improve asthma control."

Salo and co-authors, however, point out that more research is needed to understand the complex relationships between genetic and environmental factors that cause asthma, particularly the role that indoor allergen exposure plays in the development of asthma. "Although reducing allergen levels in the home may not prevent individuals from developing asthma, reducing exposure levels is crucial for those whose asthma is allergic in nature." Zeldin concluded.

Source: Salo PM, Arbes SJ, Crockett PW et al. Exposure to multiple indoor allergens in US homes and its relationship to asthma. J. Allergy Clin. Immunol. 121(3) 678-684 (2008).


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