Allergies mysteriously on rise in U.S.

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Allergies mysteriously on rise in U.S.

The number of those with allergies is 2 to 5 times higher than 30 years ago

By Rettner

LiveScience

updated 9:44 p.m. ET, Fri., March. 26, 2010

If you think you're seeing more people sneezing and tearing up this allergy

season, you might be right. Studies show that allergies are on the rise in

developed countries, including the United States — not just seasonal allergies,

but allergies of all kinds.

An allergy is a reaction of your immune system to what are usually harmless,

run-of-the-mill substances, such as pollen, cat hair, or even a peanut. About 54

percent of Americans are sensitive to at least one allergy-inducing substance,

according to a national survey conducted from 1988 to 1994 by the National

Institutes of Health (NIH). That's about two to five times higher, depending on

the allergen, than the rates found by NIH between 1976 and 1980.

The result: Americans are sneezing and wheezing and rubbing itchy eyes more than

ever.

The insurance claims that people file when they see an allergist also document

an increase, according to Dr. S. Eghrari-Sabet, an allergist at

Family Asthma & Allergy Care in Gaithersburg, Md., and a fellow of the American

Academy of Allergy Asthma & Immunology.

And food allergies in children have also experienced an uptick. From 1997 to

2007, the number of children with food allergies rose 18 percent, according to

the Centers for Disease Control and Prevention.

" You walk in to any kindergarten, and they're all peanut-free kindergarteners

because of the high incidence of peanut allergy, " said Eghrari-Sabet. " Those

kids are real, and they weren't there the generation before. "

While no one knows for sure what's fueling the increase in allergies ,

Eghrari-Sabet and others suggest some possibilities, including:

We're too clean

Cleanliness could be to blame. The " hygiene hypothesis " proposes children

aren't exposed to enough dirt, bacteria and other infectious agents early on,

and their under-stimulated immune systems goes on the offense when exposed to

benign stuff like food.

" Their 'bored' immune system goes out and attacks a peanut, an egg, wheat, milk

— foods that are in everybody's diet quite normally, " Eghrari-Sabet said.

Previous studies have shown that children in daycares, known to be hotbeds for

spreading germs, have fewer allergies than those raised at home with less

contact with other kids, said Dr. Honsinger, an allergist and

immunologist at Los Alamos Medical Care Clinic in New Mexico.

However, Eghrari-Sabet notes that while both statements are true — children are

kept in cleaner environments, and children have more food allergies than ever

before — this doesn't make the hygiene hypothesis true.

Global warming

The rise in carbon dioxide levels in the atmosphere and warming global

temperatures could also be contributing to the allergy increase.

A 2005 study found that plants are flowering earlier in the year, and total

pollen production is increasing. A more recent study in Italy found that not

only had pollen levels increased in the area, but the populations' sensitivity

to pollen had increased as well. While genetics plays a large role in all

allergies, a longer and more intense pollen season could exacerbate symptoms.

We're too dirty

All the smog and other types of air pollution might also be making allergies

worse, particularly asthma. However, while there is good evidence for the link

between pollution and allergies in a test tube, it remains tough to prove in

large populations of people, Eghrari-Sabet said.

Just more diagnoses

It's possible that the rising numbers are simply due to more people being

diagnosed with allergies, Eghrari-Sabet said. " Whereas before people were told

you just have dry skin or a rash, now they're told, you have eczema, " she said.

With better allergy treatments, more sufferers might go to their doctor, bumping

up diagnoses more. However, more diagnoses alone simply can't explain the entire

increase, especially for food allergies Eghrari-Sabet said.

Mystery remains

The real culprit remains a mystery. We're too clean, we're too dirty and

everything in between; all of these hypotheses could be operating

simultaneously, or all could be untrue.

" They're really pretty much all on the same level, and the reason for that is

because they are all equally hard to prove, " Eghrari-Sabet said.

However, Honsinger thinks that the hygiene hypothesis has the most backing in

terms of evidence, and is becoming more accepted among those in the field. But

he agrees that the rise in sniffles and sneezes remains unexplained.

" I don't think we have a single cause, and I don't know if we have an answer for

sure, " he said.

And it remains unclear if an answer will come anytime soon. Funding tends to go

toward research into what to do about the allergy increase, rather than into

what's causing it, Eghrari-Sabet said.

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URL: http://www.msnbc.msn.com/id/36060765/ns/health-allergies_and_asthma/