Food Allergy Facts

Food is supposed to help children grow up healthy and strong. But for a growing number of kids, something as innocuous as a peanut butter sandwich, a scrambled egg, or a bottle of milk can cause problems -- and that's a major source of anxiety for their parents. Between 6 and 8 percent of children younger than age 5 are allergic to specific foods, and those numbers are expected to rise. a 2010 study found that the number of children with a peanut allergy has tripled from 1997 to 2008. Researchers are still sleuthing out what's driving the increase, though they suspect that some combination of hereditary and environmental factors is responsible. Here, we answer some common questions.

Food-allergy symptoms typically occur within a few minutes to an hour after eating a food and are unmistakable: hives (red, raised welts); vomiting; diarrhea; wheezing; and swelling around the lips, tongue, or eyes are all common. In severe cases, a person experiences multiple symptoms at once in a life-threatening reaction known as anaphylaxis.

The vast majority of food allergies (90 percent) are triggered by milk, eggs, peanuts, tree nuts, wheat, soy, shellfish, and fish -- known in allergy circles as "the big eight." And if a child is allergic to one food, she's usually allergic to others, says Scott Sicherer, MD, author of Understanding and Managing Your Child's Food Allergies (Johns Hopkins University Press). Peanuts, tree nuts, and shellfish are the most likely to cause anaphylaxis.

Children who are allergic to food (or things in the environment such as ragweed and dust) have immune systems that are miscalibrated. Their immune systems mistakenly target proteins in certain foods as if they're harmful invaders to the body like bacteria or viruses. The first time your child eats the food, his immune system makes an antibody called IgE; this antibody attaches itself to cells that live in the nose, throat, lungs, skin, or gastrointestinal tract. Every time your child eats the offending food, these cells are activated to cause symptoms, such as hives that sprout on his face.

Children are more likely to have allergies if their parents are allergic. A child with one parent who has any kind of allergy, including environmental or seasonal allergies, has a 30 percent chance of becoming allergic. Having two allergic parents increases a child's risk to 60 percent.