By LEE BOWMAN
Scripps Howard News Service
August 05, 2005
The findings, based on the third National Health and Nutrition Examination Survey that included skin tests on about 10,500 people between 1988 and 1994, showed that 54.3 percent had a positive response to at least one allergen.
About 25 percent of the population tested positive for dust mites, perennial rye, ragweed and cockroaches. Peanut allergy was the least common, with 9 percent reacting to it. A positive result was defined by the size of a welt on skin compared with a prick from a negative control.
The results were published online last month and printed in the August issue of the Journal of Allergy and Clinical Immunology.
Researchers from the National Institute of Environmental Health Sciences and the National Institute of Allergy and Infectious Diseases also compared skin-test responses between the most recent survey and similar tests done in 1976-1980. They found that the prevalence of sensitivity to the six allergens that were tested in both surveys was 2 to 5.5 times higher in the later round. The earlier survey tested eight common allergens.
"An increase in prevalence is consistent with reports from other countries and coincides with an increase in asthma cases during that time," said Samuel Arbes, an NIEHS researcher and lead author of the study.
Other research indicates that the prevalence of asthma in the United States increased by nearly 74 percent between 1980 and 1996. Arbes stressed that differences in skin-test procedures between the two surveys don't allow researchers to definitively conclude that reactions to allergens are really on the rise among Americans.
"There is still much we don't understand about why some people become sensitized to allergens and others do not," said Dr. Darryl Zeldin, senior author of the study. He is also with the NIEHS.
"Much more research is needed in order for us to understand the complex relationship between exposures to allergens, the development of allergic sensitization and the onset and exacerbation of allergic diseases such as asthma."
Other allergens tested in the later round included cat dander, Bermuda grass, Russian thistle, white oak and a common airborne fungus called alternia alternata.
Positive test responses were also more likely to be seen among men of all ages, people in their 20s of both sexes, minorities and those living in older homes.
For the next national health survey, under way this year and in 2006, skin tests are again being done for about 10,000 individuals nationwide, but researchers are also analyzing dust samples from the participants' homes. Blood samples from each person will also be analyzed to see if he or she has antibodies that indicate an allergy to the most common allergens in their homes.
"Understanding what may account for the rising worldwide asthma rates will allow us to develop more effective treatment and prevention approaches," said Dr. David Schwartz, director of the NIEHS.
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