According to the American Academy of Allergy, Asthma and Immunology, about 8 percent of children have food allergies, compared to 2 percent of adults. The good news those figures reflect is that some, though not all, food allergies can be outgrown over time, particularly when they stop eating the food. Below, Jacqueline Pongracic, MD, division head of allergy, at Children's Memorial Hospital in Chicago, discusses how to recognize the signs of a food allergy, as well as how to ensure proper diagnosis and follow-up, so you can keep your child safe. What is a food allergy? It's a food reaction that happens through the immune system. That's important to understand because other types of food reactions exist, such as intolerances. An example of that would be lactose intolerance, which doesn't occur through the immune system but because of a lack of an enzyme in the gut that breaks down lactose. What is happening in the body when one has a food allergy? When someone has an allergy the immune system produces an allergy antibody that we call IgE, in response to a particular protein. Once IgE is produced, it circulates in the body until it encounters allergy cells. When the IgE encounters those cells, it attaches to them. Then the antibody waits like a guard watching for that particular protein. Let's say an individual produces IgE antibody to egg. When that sensitive individual eats egg again, the egg protein will be absorbed and when it encounters the IgE specific for egg protein, the two join together. When that happens, the allergy cells release a variety of chemicals that can cause the signs and symptoms of an allergic reaction. When do food allergies first appear? Food allergy can begin at any point in life, but most commonly it begins in the first three years of life. What foods are children commonly allergic to? The most common foods include egg, cows' milk, wheat, peanuts, soy and tree nuts. So that's a list of six foods that account for about 95 percent of reactions in children. What kinds of reactions do people with food allergy have? One of the important characteristics of reactions in food allergy is that the reaction typically occurs within minutes and always within one to two hours after eating the food. Another characteristic is that reactions occur each and every time that particular food is ingested.