What's behind this rapid increase? While we don't fully know the cause, medical data suggest it could be related to a phenomenon known as the hygiene hypothesis, says Julia Bradsher, CEO of the Food Allergy and Anaphylaxis Network. "Because children in our culture are exposed to fewer germs than their bodies are used to dealing with, the immune system is deprived of the full-time germ-fighting job they have to do, and [immune systems] misidentify food as harmful" she says.
After identifying food as harmful, the body reacts by trying to fight the food—resulting in an allergic reaction with symptoms ranging from relatively benign ones, like hives, rashes and tingling in the mouth, to terrifying ones, like swelling in the throat, difficulty breathing and loss of consciousness.
While a food allergy is caused by a misidentification by the immune system, food intolerance is a digestive problem. This is an important distinction. Because they could cause restricted breathing and loss of consciousness, food allergies are considered potentially life-threatening; food intolerances generally are not. For instance, one of the most common food intolerances is lactose intolerance, in which a person has trouble digesting the sugar in dairy products. It can result in abdominal cramps, bloating and diarrhea—not symptoms anybody would want their children ever want to experience, but not deadly.
Bradsher says it's common for children to outgrow some childhood food allergies—but some are lifelong. "Some of the allergies will go away, like milk and eggs," she says. "And the others will stay, like peanuts and tree nuts."