A true allergic reaction—when the body forms antibodies against allergens—is different and more severe than an adverse reaction to food, such as lactose intolerance, when the body has trouble digesting dairy products. While approximately 6 to 8 percent of babies will have a food allergy by a year of age, many will have outgrown them by the time they're 4 to 5 years old.
Six foods cause 90 percent of food allergies in children: dairy, eggs, peanuts, tree nuts (such as pecans and walnuts), soy, and wheat. A breastfed baby can develop a food allergy if she's exposed to an allergen (such as cow's milk or peanuts) via breast milk. Her mom can continue nursing as long as she eliminates the allergy-causing food from her own diet.
Signs of a food allergy include a rash around the face, hives, vomiting, diarrhea, trouble breathing, or swelling of the mouth and throat. The reaction usually occurs within a few minutes of eating the suspect food and can range from a mild rash to life-threatening anaphylaxis, which can cause breathing complications and loss of consciousness. Severe reactions are usually due to nut or fish allergies, and these are seldom outgrown.
An allergy to cow's milk proteins—from formula or breast milk—is common in the first year of life. Babies with a milk allergy are more likely to later develop hay fever or asthma. Many infants who are allergic to cow's milk-based formula are also allergic to soy-based formula and will need a hypoallergenic one.
Skin or blood tests can help pinpoint a child's food allergy. The results are not always easy to interpret, however, as positive results can occur without a true allergy. You may be asked to keep a chronological food diary for a few weeks, in which you write down everything your baby eats (and that you eat, if you're nursing) and any symptoms that you notice. Another method involves avoiding a suspect food for about two weeks, and then reintroducing it at the doctor's office where emergency care is available.
The first step is to eliminate the offending food from your child's diet—not so easy when you consider how many foods contain milk, eggs, or wheat, for instance. Favorites like pasta, pizza, and mac 'n cheese can become immediate no-no's. Shopping and meal preparation take longer as well if you have to wade through labels and recipes to spot hidden ingredients. By January 2006, however, manufacturers will be required to clearly label the presence of allergens in food products.
You'll also need to inform friends, relatives, and caregivers about your child's food allergy, and be prepared for an accidental exposure. Antihistamines can be given to treat symptoms, and if a severe reaction has occurred in the past, your pediatrician may prescribe epinephrine that you can administer if there's an emergency.
If you or your partner have allergies, you can lower your baby's risk by breastfeeding (if it's possible) and using a hypoallergenic formula if you're supplementing. Your pediatrician may recommend that you avoid eating common food allergens, such as milk or nuts, during breastfeeding. The American Academy of Pediatrics also recommends delaying the age at which certain foods are introduced into your child's diet: Cow's milk, wheat, and soy should be delayed for at least one year; egg white for two years; and fish, shellfish, and peanut butter for three years. (Nuts should be avoided until age 4 because they're a choking hazard.) Your doctor may even suggest that you avoid eating peanuts during pregnancy.
Even if your baby doesn't have a family history, breastfeeding can reduce the risk of allergies, as can delaying the introduction of egg white, wheat, and cow's milk until your baby turns 1, and peanut butter and shellfish until age 2. To learn more, contact The Food Allergy & Anaphylaxis Network at 800-929-4040 or www.foodallergy.org.