More than 50% of the U.S. population tested positive to one or more allergens, according to a large national study.

The new findings, based on data from the third National Health and Nutrition Examination Survey (NHANES III), shows that 54.3% of individuals aged 6-59 years old had a positive skin test response to at least one of the 10 allergens tested. The highest prevalence rates were for dust mite, rye, ragweed and cockroach, with about 25% of the population testing positive to each allergen. Peanut allergy was the least common, with 9% of the population reacting positively to that food allergen.

The new findings published in the August 2005 issue of the Journal of Allergy and Clinical Immunology were conducted by researchers at the National Institute of Environmental Health Sciences (NIEHS) and the National Institute of Allergy and Infectious Diseases, both components of the U.S. National Institutes of Health.

A positive skin test result may mean the individual is more vulnerable to asthma, hay fever and eczema. "Asthma is one of the world's most significant chronic health conditions," said David A. Schwartz, M.D., the NIEHS director. "Understanding what may account for the rising worldwide asthma rates will allow us to develop more effective prevention and treatment approaches."

NHANES III is a nationally representative survey conducted by the U.S. Centers for Disease Control and Prevention between 1988-1994 to determine the health and nutritional status of the U.S. population. Approximately 10,500 individuals participated in the skin testing. During these tests, skin was exposed to allergy-causing substances (allergens) and a positive test was determined by the size of the reaction on the skin. The 10 allergens tested include: dust mite, German cockroach, cat, perennial rye, short ragweed, Bermuda grass, Russian thistle, white oak, Alternia alternate and peanuts.

Researchers also compared skin test responses between NHANES III and the previous survey, NHANES II, conducted from 1976-1980. The prevalence of a positive skin test response was much higher in NHANES III than in NHANES II.

According to the lead author, Samuel J. Arbes, Ph.D., of NIEHS, "An increase in prevalence is consistent with reports from other countries and coincides with an increase in asthma cases during that time." In the U.S., the prevalence of asthma increased 73.9% from 1980 to 1996. However, Arbes was quick to note differences in skin test procedures between the two surveys prevent the authors from definitively concluding that the prevalence of skin test positivity has increased in the U.S. population.

"There is still much we do not understand about why some people become sensitized to allergens and others do not," said Darryl C. Zeldin, M.D., senior author on the paper. "Much more research is needed in order for us to understand the complex relationships between exposures to allergens, the development of allergic sensitization, and the onset and exacerbation of allergic diseases such as asthma."

Source: Lab Business Week