6 Theories Behind Allergies

The number of Americans suffering from allergies continues to break historic records. Though scores of theories attempting to explain the cause of this rise exist, allergists and immunologists point to 5 most likely. They are;the 'hygiene hypothesis;' antibiotics and vaccine use; environmental pollution; genetic predisposition; age-depressed immune systems and too much dairy in the diet.

Currently, half of all americans test positive for at least one of the top ten allergens. When it comes to hay fever, count 26 million Americans as sufferers. In the UK, the number of diagnosed multiple allergy patients has seen a steep rise.

"It's a steady rise and it's been happening for quite some time," said Alessandro Sette, a principal investigator at the La Jolla Institute for Allergy & Immunology.

What's behind all of this? Here are 6 theories culled from ABCNEWS and the San Diego Star Union

Theory 1: It's called, more accurately, "the hygiene hypothesis," the supposition that modern-day living is, in some ways, too clean and too safe. "Our immune systems are really cognitive systems, just like the brain and nervous system," said Sette. "It has to learn how to recognize what's OK."In today's society, however, people live more and more in an ultraclean environment, which is generally a good thing. But they aren't exposed as much now to a diversity of potential allergens. As a result, the immune system doesn't get enough stimulation. It doesn't become street smart."

Theory 2: A corollary, perhaps, of Theory #1, this posits that the widespread use of antibiotics and vaccines has diminished the need for a naturally robust immunological defense. Again, if you don't use it, you lose it. Our immune systems aren't getting exposed to enough different things on a daily basis.

Theory 3: It's all about the environment. Modern living may be cleaner, but it also exposes people to pollutants, chemicals and compounds that didn't exist years ago - at least not at current levels. Airborne pollutants can cause chronic irritation of the airways, making some people more vulnerable to other allergens. Primary culprits? Coal-fired power plants with Clean Air Act exemptions and automobiles.

Theory 4: People are genetically predisposed to particular allergies. If one of your parents has an allergy of any type, the chances are 1 in 3 that you will have an allergy, too. If both parents have allergies, your odds bump up to 7 in 10. The allergy, however, may not rear its ugly head until adulthood, until years of exposure to the offending allergen have accumulated.

Theory 5: Adults become allergic because, well, they're adults. Over time, the immune system evolves, said Sette. It usually becomes less active with age, but activity or sensitivity can go up or down depending upon myriad factors, from overall health to dietary changes.

Theory 6: Consuming too many dairy products cause allergies. This theory about cow's milk looks to be, well, bull.

"I've not seen any studies that would suggest that's a viable option," said Wesley Burks, chief of the Division of Pediatric Allergy and Immunology at Duke University Medical Center.

Burks says that while many explanations have been offered for why allergies are rising in industrialized nations but not in developing ones, the milk theory is among the weakest.

To Burks, one explanation does stand out, however.

"There aren't great reasons for [the increase in allergies] now, other than the hygiene hypothesis," he said. "The theory would be that we're living too clean a lifestyle, and that's what causes the increase in allergic disease."

"There's some good evidence from Eastern European studies," said Burks. "Children that grew up with farm animals … there's significantly less allergic disease in those children."

So while drinking cow's milk may not cause your allergies, hanging around cows as a child might just keep allergies away.

Ultimately historic highs in allergy sufferers can't be traced to a single, isolated cause. This most plausible theory behind the cause of so much sneezing is that it's a mix of the 5 factors. Like the mix of pollen, particulate matter and airborne molds we ingest into our immune-suppressedungs is a mix.

"I don't think there is any single cause," said Sette. "There are many causes and they're different for different people."

Here's an allergy survival guide done by 'CBS Healthwatch.'