Is hygiene responsible for allergy increase?

Is our obsession with cleanliness responsible for the rise in food allergies in children?

Researchers at Children's Hospital Boston found that the number of food-induced allergic reactions treated in their ER more than doubled over six years - from 164 cases in 2001, to 391 in 2006.

The findings are in line with studies pointing to a general increase in food allergies among US children in recent years, according to Dr. Susan A. Rudders, one of the authors of the study.

No one is sure why food allergies are being increasingly diagnosed, but one theory is that less exposure to germs from early life may, in some people, make the immune system more prone to attacking normally benign substances, like food proteins and pollen. This is known as the "hygiene hypothesis".

According to the US Centers for Disease Control and Prevention, 3 million school-aged children in the US had a food allergy in 2007, which was up 18 percent from 10 years earlier. Among the most common triggers of food allergies in Medical ID wearers are peanuts and tree nuts -- such as almonds, walnuts and cashews -- milk and eggs.