According to the National Review of Medicine, researchers at New York University have discovered more evidence in support of the hygiene hypothesis. The hygiene hypothesis posits that modern societies have experienced an increase in asthma and allergies because of decreased exposure to microbes due to sanitation.

Researchers found that the stomach bacterium Helicobacter pylori, or H pylori (often blamed for peptic ulcers, gastritis, and duodenitis) is actually protective against asthma and allergy.

"We went into this study with two assumptions," says Dr Martin Blaser, chairman of the NYU Department of Medicine, who has studied H pylori for two decades. "First, that H pylori would be protective against asthma, especially the cagA variant — that proved correct. Second, that the protective mechanism was linked to H pylori's known protective effect against gastrointestinal reflux disease (GERD). That proved false."

While it seems reasonable to assume that airway damage from GERD could cause asthma, the researchers also found that H pylori offers protection against skin sensitivity to allergens as well - and as Dr. Blaser says, "There seems no way that GERD could influence skin sensitization."

It appears that H pylori colonization is the default human state, but it's a state from which we're swiftly drifting.

"It's notable that people with H pylori have a large mass of gastric lymphoid tissue which plays an important role in the development of the immune system," says Dr. Blaser. "About 10% of the US population now has detectable H pylori colonization. I was just in Sweden and Germany, where I'm told the figure is less than 5%. The proportion in the developing world is over 50%, and just a few generations ago the levels in our own societies were 70, 80, even 90%. So H pylori is disappearing really fast, and this disappearance is almost certainly mirrored in other microorganisms we can't detect as easily."

"I wrote a paper on this a few years ago called Global Warming and the Human Stomach," continues Dr. Blaser, "because I wanted to point out that there is a mass extinction process taking place in our micro-environment that mirrors what we're seeing in our macro-environment. We're just beginning to look at these issues seriously. We need to know what we're doing when we upset relationships that have existed for tens of thousands of years."