|What's the Hygiene Hypothesis?|
|By EMILY DERUY (@emily_deruy )||May 1, 2013, 10:25 AM|
America's obsession with antibacterial wipes and hand sanitizer may not be such a good thing. Research shows that some exposure to germs is actually helpful.
A new study found that children born outside the U.S. develop fewer allergies than kids born in the country. And the reason isn't that they have some super resistance to them. It may have to do, instead, with the hygiene hypothesis: Kids who spend some of their earliest years exposed to infections and germs seem to get fewer allergies.
"It would be expected that immigrants to the United States from developing countries, where infectious stimuli are more prevalent, would have a lower risk of allergic disease" noted the researchers.
It might also have to do with what foods those children eat and their lifestyles. Asian children living in Chinatown, for example, have lower rates of asthma than Asians outside of that neighborhood.
While the researchers don't have a definitive answer yet, the numbers are compelling.
More than 10 percent of American kids suffer from asthma, according to the study, which was published in JAMA Pediatric, and one in five may have atopic dermatitis, a skin disease. Those numbers are high when compared to immigrant kids though. While just one in five foreign-born kids develop allergies, more than one in three U.S.-born children do. The discrepancy when it comes to asthma is even larger.
Mexican Americans born in the U.S. have significantly higher rates of asthma, for instance, than Mexican Americans born in Mexico.
Things like socioeconomic status and ethnicity can play a role, but the researchers accounted for those factors and a strong correlation between being born outside the U.S. and fewer allergies.
That fact was further bolstered by the study's finding that foreign-born kids who spend just a couple of years in the U.S. are far less likely to develop allergies than foreign-born kids who live in the country for a decade or more.
However, this could also mean that the benefits of being born somewhere else don't necessarily provide a shield after so much time has elapsed.
"The odds of developing allergic disease dramatically increase after living in the United States for longer than 10 years," wrote the researchers. "This suggests that the protective effects of the hygiene hypothesis may not be lifelong and that subsequent exposure to allergens and other environmental factors may trigger atopic disease even later in life."
The idea that those kids might be eating healthier and living lifestyles more in line with their countries of origin gains traction when you consider that foreign-born kids with U.S.-born parents are more likely to get allergies than foreign-born kids whose parents are also born outside the country.
"Some cultures more commonly use spices, such as curcumin, and green tea that have anti-allergy and inflammatory properties," wrote the scientists.
They aren't suggesting you immediately alter your kid's diet if he has allergies or to let her aversion to baths flourish, and they're certainly not saying that if your child has allergies that you should've let them roll in grass more as a toddler. But some early exposure to irritants may be a good thing.
In other words, it's ok to put down the Lysol wipes. Exposure to a few germs -- a romp through a muddy field or a splash through a puddle, for example -- may help developing immune systems learn to successfully recognize and respond to germs.