Health knowledge and news provided by doctors.

Rise in Allergies Due Mostly to Ragweed and Mold


If allergies seem to be a bigger problem than usual, you are not imagining things. Results of a national report, Allergies Across America™, note that while sensitization to numerous allergens has increased, the rise in allergies is due mostly to ragweed and mold.

Allergen increase linked to climate change

Allergies Across America, a Quest Diagnostics Health Trends™ Report, is the largest cross-sectional study of allergies ever conducted in the United States. The findings are based on the results of nearly 14 million blood tests for 11 common allergens (ragweed, mold, two house dust mites, cats, dogs, and five foods) and involved more than 2 million patient visits.

Patient information included in the study came from individuals ranging in age from infancy to 70 years and from all 50 states and the District of Columbia. The allergy test used was the ImmunoCAP® specific IgE blood test. IgE is an antibody that the body produces in response to the presence of an allergen, such as ragweed pollen.

Based on test results gathered over four years, the report’s authors noted that sensitization rates to common ragweed rose 15 percent across the nation, and mold increased 12 percent. Overall, sensitization to all 11 allergens combined climbed 5.8 percent.

Follow eMaxHealth on YouTube, Twitter and Facebook.

According to Stanley J. Naides, MD, medical director, immunology at Quest Diagnostics, they believe theirs 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.”

Up to 20 percent of Americans are sensitive to ragweed, a genus of hardy plants in the sunflower family. There are 41 species around the world, and they tend to thrive in dry climates.

With a warming climate, longer blooming seasons can be expected, along with an increase in environmental allergens, such as ragweed. Mold is also affected by climate, and its prevalence can increase as temperatures rise.

Individuals who are allergic to ragweed might take interest in the report’s ranking of the 30 most populous cities in the United States for sensitization to the allergen. Rounding out the top five worst cities are Phoenix (no. 1), followed by Las Vegas, Kansas City, Riverside-San Bernardino (CA), and Dallas.

It appears that one of the side effects of global warming may be an increase in allergies, and in the United States, ragweed and mold sensitization is rising. Naides noted that “Given concerns about a warming climate, additional research is needed to confirm these findings and assess the possible implications for public health.”

Quest Diagnostics Health Trends Report