John A. Allocca, D.Sc., Ph.D.
May 13, 2014
This allergy season could be worse than those of past years in the U.S. because of heavy snow and rain in many places, followed by a sudden shift to warm weather, have led to a profusion of tree pollen and mold. Springtime is arriving 10 to 14 days earlier than it did 20 years ago, which results in higher pollen levels for longer periods of time.
Allergy seasons have been getting longer, although pollen counts and allergy attacks vary widely from region to region. Pollen from trees, weeds and grasses are the primary culprits behind seasonal allergies.
A new study in the Proceedings of the National Academy of Sciences shows a link between warming temperatures and a longer ragweed pollen season. According to researchers led by Lewis Ziska of the U.S. Department of Agriculture, the ragweed season is now 27 days longer in the northernmost areas of North America, largely because winter starts later and ends earlier, extending the time for pollen-bearing plants to thrive. It's not the first piece of research to make the claim that global warming will worsen allergies, but it's the most detailed and it's peer-reviewed.
Clifford Bassett, MD, medical director of Allergy and Asthma Care of New York uses the example of ragweed, a very common allergen. Under normal circumstances, a single ragweed plant produces 1 million pollen grains. However, a CO2-rich environment boosts that number to 3 to 4 million grains. And ragweed is only ONE of the weed species making people miserable - there are many others that scientists expect to become "supercharged" by Earth's warming climate.
Allergies are the body's reaction to allergens (particles the body considers foreign), a sign that the immune system is hyperactive. The first time the body encounters an allergen, the plasma cells release IgE (immunoglobulin E), an antibody specific to that allergen. IgE attaches to the surface of mast cells. Mast cells are found in great numbers in the surface tissues. Mast cells release a number of important chemical mediators, one of which is histamine.
The second time the body encounters an allergen, the mast cells become activated within a few minutes and release histamine, leukotrienes, and prostaglandins, which trigger such symptoms as: sneezing, runny nose, sore throat, cough, itchy eyes, etc. Histamine can cause airways to constrict, like with asthma, or cause blood vessels to become more permeable, leading to fluid leakage or hives. Leukotrienes cause hypersecretion of mucus, which is commonly experienced as a runny nose or increased phlegm.
People usually outgrow their seasonal allergies by the time they reach the age of 60 to 70, when their immune systems become less reactive.
Besides pollen, household chemicals such as triclosan and bisphenol-A (BPA) can aggravate or even cause allergies. Scientists from the University of Michigan recently found that people who commonly used triclosan products were more likely to suffer from allergies or hay fever. For this reason, avoid using antibacterial soap.
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