Allergies? Good Chance It's Ragweed Pollen; Report Suggests Climate Change a Factor

Climate change could be behind rising levels of ragweed allergies.

ByKIM CAROLLO, ABC News Medical Unit
May 26, 2011, 3:50 PM

May 27, 2011— -- Sneeze. Cough. Wheeze. Repeat.

Up to 20 percent of Americans suffer their way through the spring and summer because of ragweed allergies, and new research says the problem could be getting worse. Global warming and climate change, experts say, could be causing higher levels of ragweed in the air.

A report by Quest Diagnostics, a company that provides diagnostic testing services, suggests that allergies are on the rise nationwide, mostly due to an increase in the amount of ragweed and mold in the environment.

The company evaluated 14 million blood test results from about 2 million patients over a four-year period. Each test determined sensitivity to a specific allergen, and the company looked at 11 different allergens. They said people's sensitivity to ragweed increased 15 percent and mold sensitivity grew 12 percent.

"We believe this is the first large national study to show that the growing prevalence of allergies, suggested by other studies, is largely due to increases in environment-based allergens previously associated with climate change," said Dr. Stanley J. Naides, Quest's medical director of immunology.

The study also ranked the 30 worst metropolitan areas for ragweed allergies. They said Phoenix, Las Vegas, Kansas City, Riverside-San Bernardino, Calif. and Dallas topped the list.

Experts not associated with the report or with Quest Diagnostics have said this year's allergy season could be the worst in years. They attribute a lot of it to weather extremes in certain parts of the country. But they question the ability of blood tests to suggest reliably that a person is allergic to ragweed, mold or anything else.

"Having a positive blood test to an allergen does not equal clinical presentation of allergy," said Dr. James Sublett, managing partner of Family Allergy and Asthma in Louisville, Ky. "Allergy skin testing is still considered the gold standard by trained, board-certified allergists."

The blood test used by Quest, called ImmunoCAP, is manufactured by Phadia, one of its vendors. The test determines whether antibodies for a certain allergen are present in the blood, which the company says is "highly suggestive" of an allergy, though a full medical evaluation is necessary for an allergy diagnosis.

Dr. Stanley Fineman, president-elect of the American College of Allergy, Asthma and Immunology (ACAAI) says more and more primary care physicians and pediatricians are relying on blood tests to diagnose allergies.

"Unfortunately, the proper evaluation of a patient involves much more than just a simple blood test and there have been many examples of misdiagnosis and improper diagnosis," he said.

Fineman said Quest's research isn't peer-reviewed, meaning that other medical experts haven't reviewed the findings for themselves to evaluate whether they're significant. He said Quest may have a conflict of interest, trying to promote the blood test.

"Physicians and scientists rely on peer-reviewed journals to report carefully designed protocols to be enable the analysis of factual studies and determine ... the impact for patient care."

Quest's medical director, Dr. Harvey Kaufman, defended the report, saying allergists who look unfavorably on blood testing for allergies base their opinions on older studies that evaluated older tests.

"More recent studies have shown that some newer tests like ImmunoCAP are more reliable than skin prick tests," he said.

Are Climate and Weather to Blame?

Allergists also say the results highlighted in the report cannot accurately predict whether there really is an increase in the amount of ragweed or mold in the air.

"A rising trend in ragweed allergies is entirely different from a rise in ragweed allergen," said Dr. Harold Nelson, a senior staff physician at National Jewish Hospital in Denver. "One is related to air sampling for pollen and one to [antibody] sensitization of patients, usually ascertained by skin testing."

Ragweed is most common along the East Coast and in the Midwest. Ragweed and other pollens have been present in record amounts in certain parts of the country because of the unusually heavy rainfall.

"Winter and spring precipitation have created a 'perfect storm' for heavy pollen levels and molds," said Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York. "Higher pollen levels [have] in part [been] from increased carbon dioxide (greenhouse gases) that supercharge plants, trees, etc. to produce and release more pollen."

Experts also say ragweed seasons are getting longer, especially in the Southwest, where it can plague allergy sufferers well into the fall.

Whether ragweed levels are truly higher and whatever may be causing them, it's going to be a very long summer -- and possibly fall -- for millions of Americans.

"The allergic epidemic is here to stay," said Bassett.