Facts about Food Allergies

What Happens During an Allergic Reaction?

We've all heard scary stories about children who have life-threatening allergies to peanuts. Thankfully, not all food allergies are that serious. But experts say they are on the rise, which is why it's crucial for all parents -- especially those with babies -- to educate themselves now.

An allergic reaction to food occurs when the body's immune system mistakes a particular food for a harmful foreign substance and releases chemicals to fight it off. The most common culprits are cow's milk, eggs, peanuts, soy, wheat, tree nuts, fish, and shellfish -- and the only solution is to avoid the food altogether. Here, Hugh Sampson, M.D., chief of pediatric allergy at Mount Sinai School of Medicine, in New York City, answers some key questions about why food allergies happen and how you can help your child avoid them.

It seems like so many kids have food allergies. How common are they?
In the first three years of life, 5 to 7 percent of children have them, but the figure drops to about 2 percent by age 10. Many kids outgrow allergies to soy, wheat, and cow's milk by age 4, when their immune systems have matured a bit. Overcoming a peanut or shellfish allergy, however, is much rarer.

How do you know if your child is allergic to a certain food?
An allergic reaction often involves more than one organ, so your child might develop an itchy rash or hives on her skin, respiratory symptoms like a stuffy nose and wheezing, or gastrointestinal symptoms like vomiting or diarrhea. If your child gets only stomach symptoms, your pediatrician will probably first check for a virus or a food intolerance, which is different from an allergic reaction. Most children's first reaction to an allergen will be minor, but some kids react very seriously the first time.

What's the healthiest plan for starting a baby on solids?
To help avoid food allergies, I strongly encourage parents from allergic families to postpone solids until their baby is 6 months old, when his immune system has become more mature. If you have to introduce them sooner, try not to start before 4 months. Feed your child rice cereal first. Then go on to yellow vegetables, then fruit, and so on. You can slowly work in other types of grain, like wheat. And wait four or five days before introducing another food. Don't give your baby cow's milk or other dairy products until he's a year old, and don't introduce eggs, which are pretty allergenic, until 18 to 24 months. If you see a reaction, tell your pediatrician; you should probably wait a few months before giving that food to your child again.

Do food allergies run in families?
Yes. If you've got one child with allergies, your other children are at a much higher risk. And if you or your spouse has any sort of allergy, whether it's to food or dust mites -- or even if you have asthma -- that raises your child's risk as well. There's also a link to eczema: One of our studies showed that 40 percent of kids with moderate to severe eczema have a food allergy too.