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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

How do allergy drugs work?

The most common kind of allergy drugs are antihistamines. Histamine is a chemical messenger that triggers allergy attacks by flipping switches on cells called histamine receptors. Antihistamines block these receptors.

But they can't block every histamine receptor on every cell, says Donald J. Dvorin, MD, an allergist with The Asthma Center in Philadelphia and director of the AAAAI pollen reporting stations in Philadelphia and Cherry Hill, N.J.

"The problem is they don't go to every cell," Dvorin tells WebMD. "And the blockade is only short term -- it only works for a certain half-life."

Intranasal antihistamines work a little better. They, too, block histamine receptors. But Dvorin says they also stabilize the membranes on mast cells, preventing the release of allergy-promoting factors and reducing swelling.

A third kind of allergy drug is a corticosteroid nasal spray. This drug has a more global effect on mast cells, suppressing their activity. They block the release not only of histamine but of other allergy-promoting factors.

What is the best treatment for pollen allergy?

The very best treatment for pollen allergy is to avoid pollen, Dvorin says.

"I can't tell you how many patients tell me that as soon as they go into an air-conditioned space, their symptoms get better," he says. "They know they can't be outdoors from 5 a.m. to 11 a.m. The morning is when the pollen is released most intensely. And there is a secondary peak after 4 p.m. for certain trees and grasses."

Different allergy drugs work best for different people. But in a 2010 analysis of clinical trials by Cleveland Clinic researchers, intranasal corticosteroid drugs worked nearly twice as well as oral and nasal antihistamines, which seemed to have about the same effect.

Dvorin notes that a person needs to take intranasal corticosteroids for three to seven days "before they really work."

He advises people who know they have spring allergies to see an allergist in the off season. Skin testing can reveal which types of pollen a person is allergic to -- allowing that person to begin treatment before those plants start to release pollen in the spring.

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