Pollen `Explosion¿ Has U.S. Sneezing

Pollen has choked most of the U.S. in an unusually intense
spring allergy season.

Is it the worst ever? What can you do about it? Which allergy treatments
work best, and how do they work? Prepare for some surprises in WebMD's
pollen/allergy FAQ.

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

In some parts of the U.S. -- the tree-lined city of Atlanta, for example --
the amount of tree pollen in the air hit near-record levels.

"It's a pollen explosion," Weather.com meteorologist Tim Ballisty tells
WebMD. "In Atlanta, the pollen count was up in the 5,000s, when 120 is a high
level. And other cities in the Southeast, the Midwest, and the Northeast had
off-the-charts pollen levels, too."

What happened? A "perfect storm of conditions conducive to bring pollen into
the air," arborist Peter Gerstenberger, senior advisor to the Tree Care
Industry Association, tells WebMD. "It has a lot to do with temperatures over a
period of time that can cause a tree to create a lot of pollen. It has a lot to
do with wind speed, and it has a lot to do with precipitation."

This perfect storm, Ballisty says, had several ingredients:

• A long, cold winter dumped huge amounts of snow and rain across much of the
  nation. Trees got plenty of water, unlike recent drought years in the
  Southeast.


• Spring arrived late. When it came, it brought hot, dry, summer-like
  conditions "compressing the pollen season," according to horticulturist Amanda
  Campbell of the Atlanta Botanical Garden. Ballisty notes that this April broke
  1,800 high-temperature records across the nation.


• Spring was summer-like not only because temperatures were unusually high,
  but because a ridge of high pressure funneled moisture away from the eastern
  half of the nation for extended periods. Rain washes the pollen from the air.
  Although pollen levels quickly rebound after rain, dry periods keep pollen
  blowing in the wind.

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 rotein 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.

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.

There's also a "priming effect," in which people become more and more
sensitive to the pollen they're allergic to as the season goes on.

"Starting corticosteroid treatment early actually prevents the priming
effect," Dvorin says. "If you treat early enough you reduce symptoms.
Corticosteroids are the only products that prevent the peak of symptoms."

Allergy sufferers who get too little relief from allergy drugs may wish to
consult an allergist about getting allergy shots, which can desensitize a
person to the pollens to which they're allergic.

By Daniel DeNoon
Reviewed by Laura Martin
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