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Allergy Sensitivity Doubles Since 1970s Scientists

Don't Know What's Behind Increase By Elizabeth Weise, USA TODAY

Allergy Sensitivity Doubles Since 1970s Scientists Don't Know What's Behind Increase By Elizabeth Weise, USA TODAY

As Americans' sensitivity to allergens increases, scientists debate whether environment or lifestyle changes are to blame.

(Aug. 8) -- More than half of all Americans test positive in response to one or more allergens, double the percentage who did 30 years ago, a new study reports.

Researchers at the National Institutes of Health found that 54% of people tested positive to at least one of 10 allergens. The highest response was to dust mites, 27.5%. The lowest was to peanuts, 8.6%. The findings appear in the August issue of the Journal of Allergy and Clinical Immunology.

Researchers analyzed data from skin-prick allergy tests on 10,500 people by the Centers for Disease Control and Prevention.

The number of positive reactions is much higher than cases of actual allergic disease, notes lead researcher Samuel Arbes of the National Institutes of Health. Though a positive skin test for allergens such as ragweed or cats doesn't necessarily mean a person has or will develop allergies, there is a strong association between the two.

About 20% of U.S. residents have allergies or hay fever; 8% to 10% have asthma.

The doubling of the prevalence of the six allergens tested in the earlier survey corresponds to a period during which there also was a 74% increase in asthma, Arbes says. Though there is evidence asthma rates have peaked, allergy rates appear to still be increasing, he says.

Allergy Exam 101

You Should Ask...
· Describe your symptoms.
· Seasonal? Indoors or outdoors?
· Do you smoke?
· What type of heating system do you have?
· What medication do you take?
· What's causing my allergies?
· Should I change my lifestyle?
· How can I tell if it's allergies or flu?

The testing was part of CDC's third National Health and Nutrition Examination Survey from 1988 to 1994 and is considered the most complete national data available to scientists. The previous survey was from 1976 to 1980.

Those at highest risk of showing allergic response were people ages 20 to 29, males, minorities, people living in the West, people living in old homes and people who were not exposed to cigarette smoke.

Skin tests involve applying an allergen extract to skin, which is then lightly scratched. If the area swells, the patient has antibodies to the allergen.

Researchers don't know why positive skin tests, allergy and asthma are increasing. One theory is that people simply don't go outside as often - Americans spend an estimated 90% of their time indoors - and have higher exposures to indoor allergens.

Another theory is that children become more vulnerable when they are exposed to fewer bacteria and viruses. Some researchers believe that has an effect on the developing immune system.