National Institute of Environmental
Health Sciences (NIEHS)

For Immediate Release
Friday, February 29, 2008
Contact:
Robin Mackar
919-541-0073
rmackar@niehs.nih.gov

Increased Allergen Levels in Homes Linked to Asthma

Results from a new national survey demonstrate that elevated allergen
levels in the home are associated with asthma symptoms in allergic
individuals. The study suggests that asthmatics that have allergies
may alleviate symptoms by reducing allergen exposures inside their
homes. The work was carried out by researchers at the National
Institute of Environmental Health Sciences (NIEHS), the University of
Iowa, Rho Inc., and the Constella Group. 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, M.D., a Principal
Investigator in the Laboratory of Respiratory Biology at NIEHS and
senior author on the paper.

Asthma is one of the most common chronic ailments in the United
States, affecting more than 22 million people. Asthma has been shown
to be triggered by a wide range of substances called allergens.

The findings, published online and available in the March issue of the
Journal of Allergy & Clinical Immunology, show that exposure to
multiple indoor allergens was common in U.S. households with 52
percent having at least six detectable allergens and 46 percent having
three or more allergens at increased levels. The indoor allergens
studied included those from dog, cat, mouse, cockroach, dust mite, and
the fungus Alternaria.

The researchers used data from the National Survey of Lead and
Allergens in Housing (NSLAH) to examine factors that contribute to
high allergen levels in homes and to determine whether elevated
household allergen levels were associated with occupants' asthma
status. The NSLAH, which was the first study to characterize how
allergen exposures vary in homes at the national level, surveyed the
homes of nearly 2500 individuals in 75 locations throughout the U.S.
The survey was jointly funded by the NIEHS and the U.S. Department of
Housing and Urban Development.

Several factors were found to contribute to the increased
concentrations of allergens, including race, income, type of home, and
sources of allergens, such as 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 Päivi Salo, Ph.D., 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."

This finding is the first to provide information on total allergen
burden in U.S. homes and how it relates to asthma. "This study
confirms that indoor allergens play a major role in asthma," Zeldin
stated.

Salo and her 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.

The primary mission of the National Institute of Environmental Health
Sciences (http://www.niehs.nih.gov/) (NIEHS), one of 27 Institutes and
Centers at the National Institutes of Health, is to reduce the burden
of human illness and disability by understanding how the environment
influences the development and progression of human disease. For
additional information, visit the NIEHS Web site at http://www.niehs.nih.gov/
or for more specific information about asthma, please visit
http://www.niehs.nih.gov/health/topics/conditions/asthma/allergens.cfm.

The National Institutes of Health (NIH) -- The Nation's Medical
Research Agency -- includes 27 Institutes and Centers and is a
component of the U.S. Department of Health and Human Services. It is
the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit www.nih.gov.