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Like all allergies, hay fever stems from a glitch in the immune system. Instead of attacking harmful foreign substances such as bacteria and viruses, it tries to neutralize “invaders” that ordinarily are quite harmless -- in this case weed pollen grains that fill the air from August through October (up to the first frost).
In someone with hay fever, inhaling these tiny particles triggers a cascade of biochemical reactions, resulting in the release of histamine, a protein that causes the all-too-familiar symptoms. In addition to sneezing, congestion, and fatigue, histamine can cause coughing; post-nasal drip; itchy eyes, nose, and throat; dark circles under the eyes; and asthma attacks.
Ragweed: The Prime Cause of Fall Allergies
Many plant varieties can cause hay fever, but the 17 varieties of ragweed that grow in North America pose the biggest threat. Three out of four people who are allergic to pollen are allergic to ragweed.
A hardy annual, ragweed thrives just about anywhere turf grasses and other perennials haven’t taken root -- along roads and riverbanks, in vacant lots, and so on. Over the course of a single year, one ragweed plant can produce a staggering one billion grains of pollen. And it doesn’t fall harmlessly to the ground. It floats on the breeze. Pollen has been found hundreds of miles out to sea and two miles up into the atmosphere.
Given the profusion of pollen, is there anything hay fever sufferers can do to limit their misery?
Conventional wisdom says that hay fever sufferers should stay indoors during morning hours, because pollen counts are highest then. Not so, says Neil Kao, MD, assistant professor of medicine at the University of South Carolina School of Medicine in Greenville. “I’ve reviewed 50 years of medical literature on this, and there is simply no proof that hay fever sufferers can minimize their symptoms by staying indoors or going outdoors at certain times of day. This is a myth that even many general physicians believe.”