Skin Test Positive For At Least One Allergen
More than half of the population of the United States tested positive to one or more allergens in a large national study conducted by the National Institute of Environmental Health Sciences (NIEHS) and the National Institute of Allergy and Infectious Diseases.
 
Based on data from the third National Health and Nutrition Examination Survey (NHANES III), the new finding shows that 54.3 percent of individuals aged 6-59 years old had a positive skin test response to at least one of the 10 allergens tested.
 
Of the 10 allergens tested for the highest prevalence rates were for dust mite, rye, ragweed, and cockroach, with about 25 percent of the population testing positive to each allergen. Peanut allergy was the least common, with only nine percent of the population reacting positively to that food allergen.
 
The new findings were published in the August 2005 issue of the Journal of Allergy and Clinical Immunology.
Scientists said a positive skin test result may mean the person 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, MD, the NIEHS Director. "Understanding what may account for the rising worldwide asthma rates will allow us to develop more effective prevention and treatment approaches."
 
According to a NIH news release, NHANES III is a nationally representative survey conducted by the 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.
 
Ten Allergens Tested
During these tests, skin was exposed to allergy-causing substances and a positive test was determined by the size of the reaction on the skin. These are the 10 allergens tested. Half of the U.S. is sensitive to at least one of these:
 
- Dust mite
- German cockroach
- Cat
- Perennial rye
- Short ragweed
- Bermuda grass
- Russian thistle
- White oak
- Alternia alternata (a type of mold)
- 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 percent from 1980 to 1996. However, Dr. Arbes said that 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.
 
Exposures to Allergens
"There is still much we don't understand about why some people become sensitized to allergens and others do not," said Darryl C. Zeldin, MD, 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."
 
The researchers recently added an allergy component to NHANES 2005-2006. In addition to the other NHANES data collection components, dust samples from the homes of 10,000 individuals are being analyzed for allergens, and blood samples taken from these individuals are being examined for antibodies to those allergens. This new NHANES 2005-2006 allergy component will allow researchers to gain a greater understanding of asthma and the roles that indoor allergens play in asthma and other allergic diseases.
 

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