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Allergies Health Center

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Pollen 'Explosion' Has U.S. Sneezing

FAQ on Pollen and Allergy: Some Surprising Answers

Is the 2010 spring pollen season the worst ever for allergy sufferers? continued...

As of mid-April, Kress says, SDI calculates that about 24.7 million Americans have been affected by pollen and, to a much smaller extent, mold. Last year at this time, the number was a bit higher: about 24.8 million spring allergy sufferers.

"Pollen counts are useless. What does a count of 2,000 really mean? So we say look at the number of people affected," Kress says. "And in certain parts of the country, like the Northeast, where it seems everyone says they're dying from the pollen, the rest of the country is about the same. ... It's just that in certain areas of the country, pollen just exploded."

Why does pollen cause allergies?

Of all the things that cause allergic reactions, pollen is the most widespread. Why? Mainly because it's so hard to avoid.

Few people are allergic to the heavy, waxy pollen from large flowers because it's carried by bees and other insects. But many trees and grasses use a much more primitive form of sexual reproduction: They literally cast their pollen to the winds so it will drift onto the plants' female sex organs.

Pollen from such trees and grasses is tiny, light, and dry -- perfect for floating on the wind, and, unfortunately, perfect for getting inhaled into your nose or stuck in your eye.

Once pollen sticks to your nose or eye, it releases the protein inside it. It's this protein that triggers allergic reactions.

There are two steps to this process. First, a person has to be sensitized to a particular pollen. The pollen protein is recognized by the immune system as a foreign invader and it makes a particular kind of antibody -- IgE -- to fight it off.

The second step occurs only in people already sensitized to a specific pollen protein. When the protein hits the nose or eye, a flood of IgE antibodies travel to mast cells in the nose. The IgE sits on the outside of mast cells and, when triggered by pollen protein, unleashes a flood of histamine and other factors that cause the immune responses we know as allergy.

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