An upset tummy, a rash, or difficulty breathing are common signs of food allergies in babies. Learn what to do if you suspect this common phenomenon.

By Kaitlin Bell and Elissa Sonnenberg
Updated March 27, 2020
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It's estimated that food allergies affect up to 6 percent of children aged 0-2 years, according to The American Academy of Allergy, Asthma & Immunology (AAAAI). For these kids, eating certain foods triggers an immune system overreaction that can cause anything from chronic itching and eczema to sudden difficulty breathing and even life-threatening anaphylactic shock.

The problem is growing—the incidence of food allergies increased 50 percent between 1997 and 2011. Scientists aren't sure why, but theories include greater awareness among parents and doctors, lower immunity because of less exposure to bacteria, and lack of exposure to common allergens early in life. 

Here’s everything you need to know about food allergies in babies.

What Causes Food Allergies in Babies?

Doctors don't fully understand why some children develop food allergies and others don't. However, "eczema is one of the earliest markers of an allergic person," says Amal H. Assa'ad, M.D., a professor of pediatrics and director of Cincinnati Children's Hospital Medical Center's Food Allergy Clinic. In fact, up to 40 percent of babies with moderate to severe eczema also have food allergies, according to research by Parents advisor Hugh Sampson, M.D., director of the Jaffe Food Allergy Institute at Mount Sinai Hospital, in New York City.

A family history of eczema, asthma, and allergies also raises the stakes. "You may inherit the susceptibility to become allergic. It's not anything that the mother does when she's pregnant or breastfeeding or anything that the father does," says Dr. Assa'ad. Some children just get a bigger share of the genes that predispose them to food allergies.

The Signs of Food Allergies in Babies

In a food allergy, the immune system reacts to a harmless food as if it were a threat and creates histamines and antibodies to fight it. "All that means is that his digestive system isn't able to comfortably handle it," says pediatrician Gwenn Schurgin O'Keeffe, M.D.

Symptoms range from a tingling in the mouth and swelling of the tongue and throat to difficulty breathing, hives, vomiting, abdominal cramps, and diarrhea. Red blood in the diaper can be a sign of allergic colitis, a type of milk allergy that irritates the colon. The most serious allergic response is anaphylaxis, a potentially fatal reaction that produces a form of shock. "If your baby has trouble breathing, a swollen tongue, and becomes flushed and wheezy, don't drive to the hospital—call an ambulance immediately," warns Dr. O'Keeffe.

Every exposure to the trigger may increase the reaction's severity. And it doesn't matter if your 2-month-old has never tasted peanuts, for example: If you had a peanut butter sandwich for lunch, she can be exposed to it through your breast milk or your skin, explains Dan Atkins, M.D., a pediatric allergist at Denver Children's Hospital and National Jewish Health.

As their immune systems mature, most children outgrow allergies to egg and milk by the time they enter elementary school. Food allergies can be triggered at any age, even after a food has been ingested for years, but allergies to peanuts and different types of fish are typically the most life-threatening and often manifest themselves early and last for life. 

The Most Common Food Allergies in Babies

Because babies don't typically eat a wide range of foods, the most common allergies are to cow's milk, notes Scott H. Sicherer, M.D., of the Jaffe Food Allergy Institute at Mount Sinai School of Medicine, in New York City. Up to 7 percent of infants have trouble digesting milk. Many parents confuse this with lactose intolerance, an inability to digest the milk protein lactose that is common in older kids and adults. But this condition is rare in infants; it sometimes shows up temporarily after a stomach virus but quickly goes away.

Other common food allergies in breastfed babies (or babies who have started solids) include eggs, nuts, peanuts, wheat, soy, fish, and shellfish. Some babies have also difficulty digesting gluten—the protein in wheat, rye, and barley. "You won't detect this until your child is around 6 to 9 months old and eating more grains," says Carla Davis, M.D., a pediatric allergist and immunologist at Texas Children's Hospital, in Houston. (Celiac disease, a serious form of gluten hypersensitivity, usually doesn't show up until later.) It's rare, but some babies have intolerances to fructose (fruit sugar) and sucrose (table sugar)

How to Diagnose Baby Food Allergies

While young food-allergy sufferers number in the millions, Dr. Sicherer stresses the importance of securing a trustworthy diagnosis before drawing any dietary conclusions. Restricting a baby's diet without your pediatrician's guidance carries risks of its own. "The biggest danger is that you create a child who has a narrow range of food choices," says Frank Greer, M.D., past chair of the American Academy of Pediatrics (AAP) committee on nutrition and professor of pediatrics at the University of Wisconsin Medical School, in Madison.

If your baby has stomach problems or is fussy after meals, talk to your pediatrician and visit an allergist. Sometimes the problem isn’t related to food allergies at all: "I consider many issues," says Dr. O'Keeffe. "When babies don't take well to formula, incorrectly mixing the powder (not striking the right balance of water to formula) is a common cause. In a nursing infant, we look at the mom's diet to see if what she's eating could be producing extra gas. Overfeeding can cause similar symptoms."

Your pediatrician may have you eliminate items one by one from your baby's diet—or from your own, if you're breastfeeding—to figure out the problem food. Some doctors also recommend a skin prick test, in which an allergist pricks food-protein extracts into your baby's skin to see which ones cause a red, itchy bump. (But note that skin testing isn’t usually conducted on infants younger than 6 months).

If your baby is diagnosed with an allergy, you'll have to steer clear of her trigger foods. If it’s milk-related, doctors will usually put formula-fed babies on a hypoallergenic formula. Just remember, while food allergies can be frustrating and even scary, they don't necessarily last forever, says Parents advisor Dr. Sampson. Many kids grow out of them by age 5.

Can You Prevent Food Allergies When Pregnant and Breastfeeding?

In the past, conventional wisdom held that avoiding highly allergenic foods during pregnancy and breastfeeding— as well as withholding them from a child during his early years—could reduce his risk for food allergies. But recent evidence has turned that advice upside down. Now it seems there may be no reason to say no to allergenic foods. 

If you’re pregnant, it's OK to eat highly allergenic foods unless you are allergic to them. There’s no proof that staying away from them lowers allergy risks in babies. In fact, cutting them from your diet may cause more harm than good, as most allergenic foods provide crucial nutrients for you and your baby. For example, omega-3 fatty acids in fish and shellfish promote fetal brain development, and the folate in peanuts helps prevent neural-tube defects, such as spina bifida.

What’s more, avoiding allergenic foods while breastfeeding has not been shown to provide any benefit to your baby. However, researchers do believe that breastfeeding itself may help ward off food allergies. "Exclusive breastfeeding—no formula—for four months or longer is the best thing," says Dr. Greer. If your breastfed baby reacts to something you eat, avoid it. 

As for the opposite tactic—going out of your way to eat allergenic foods during pregnancy or breastfeeding— there's no evidence that doing so offers any protection against allergies either, Greer says

Smart Feeding Strategies for Starting Solids

According to the American Academy of Pediatrics, offering your baby allergenic foods is OK starting at four to six months; just be sure to watch for any allergic reaction (symptoms include hives, itchy eyes or mouth, vomiting, pale skin, fainting, difficulty breathing and swelling of the eyes, tongue, or lips). 

Indeed, “several studies show that the early introduction of highly allergenic food can lead to a lower rate of food allergies,” says Katie Marks-Cogan, M.D, co-founder and Chief Allergist of Ready, Set, Food. “This age lets you mold the immune system away from allergies.”

Introduce new foods one at a time, two to three days apart. Record everything that your baby eats for several weeks as well as any related symptoms (eczema, fussiness, gas). Visit your doctor if you notice a concerning pattern. 

If your infant is diagnosed with asthma, eczema, or a food allergy, follow your doctor's instructions on the timing of solid foods, says Dr. Greer.

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