Facts about Food Allergies

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.

So if I'm pregnant and have a history of seasonal allergies, are there any preventive steps I can take?
Yes. We recommend that women with allergies stay away from highly allergenic foods, like peanuts, while they're pregnant. There is some data that suggests that babies can be sensitized to certain foods in utero. Taking preventive steps during breast-feeding may be even more helpful. We now recommend that nursing moms stay away from peanuts, tree nuts, and shellfish, but they should not avoid milk and eggs, since both contain vital nutrients. And don't skip breast-feeding altogether if you're concerned about food allergies; breast milk does have a protective effect on a baby's immune system. But if your baby develops a rash or colic or spits up while nursing, ask your doctor whether something in your diet may be the cause.

Let's talk about peanut allergies, which can produce especially severe reactions. Will a child who's allergic to peanuts be that way his whole life?
That's what we used to think. However, a recent study done in England and a study I did with colleagues at Johns Hopkins, in Baltimore, showed that about 20 percent of children under the age of 4 do outgrow their peanut allergy. But if they are still reacting to peanuts after age 4, the chance of their ever outgrowing the allergy is pretty small.

Kids with peanut allergies are at high risk for anaphylactic shock, in which the throat swells up and breathing stops. How common is it?
It's estimated that about 30,000 cases of food-induced anaphylactic shock are treated in emergency rooms each year. Any parent whose child has an allergy this severe should always carry a shot of epinephrine to slow the reaction until the child can get to the E.R.

So when is an appropriate time to start giving a child peanut butter?
If there are no allergies in the family, wait until the child is 2. If one of the parents, especially the mother, has any sort of allergy, then I suggest avoiding peanut butter until age 3. This may determine whether a child develops a lifelong peanut allergy or not.

Are lots of parents really feeding it to kids younger than that?
It's amazing. What's really popular are those orange-cracker snacks with the peanut butter inside. In one study, 80 percent of the children observed had eaten peanut butter by age 1, and 100 percent had had it by age 2, even though their parents were told not to feed their kids peanut butter at all until age 2.

When should parents take their child to see a pediatric allergist?
If we can diagnose an allergy in a child within the first year or so and remove the food from her diet, I believe she's more likely to lose her sensitivity to it.

Will there ever be a food-allergy cure?
Right now we're testing a monthly shot for peanut allergies. You'd need to take it for the rest of your life, but if it proves to be effective, it would protect against all kinds of food allergies. We are also just beginning work on developing a peanut-allergy vaccine.

For more information on food allergies, check out our Food-Allergy Resource Guide.

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