Is Your Breastfed Baby Allergic to Milk?

If your baby becomes gassy and irritable after nursing, they might be allergic to the dairy in your diet. Here's what you need to know about cow's milk allergies in breastfeeding babies. 

It's normal for both breastfed and formula-fed babies to get gassy and irritable sometimes. But if these symptoms often appear in your breastfed baby after feedings, your baby might be having a negative reaction to something you’re eating that's making its way into your breast milk.

"Most [nursing parents] are able to eat anything they like during breastfeeding and experience no issues," says Molly Petersen, certified lactation counselor (CLC) at Lansinoh. But occasionally, particles from food might "leak" into your baby’s bloodstream through nursing, and their immune system might overreact to these unfamiliar substances.

While plenty of foods can cause baby allergies, one of the most common culprits is cow’s milk. That’s because the protein molecules in dairy can trigger sensitivity. (Lactose isn’t a problem since babies are made to digest the lactose in human milk.) Here’s how to recognize and treat milk allergy in breastfed infants.

Is My Baby Allergic to Milk?

Babies can develop food sensitivities that come and go throughout their first year because of their immature immune systems. An infant might also have an allergy to certain trigger foods. These scenarios are especially common if you have a family history of food allergies, eczema, or asthma.

According to clinical data, babies with cow's milk allergies usually present symptoms before 6 months of age. Those symptoms can vary depending on the severity of the allergy and will appear as either rapid onset symptoms (they appear within an hour of ingesting milk) or slow onset symptoms (they take hours to appear).

Frustratingly for some parents, symptoms can occasionally appear days or weeks after ingesting, too, making it essential to talk to your baby's doctor to determine which type of allergy severity you're dealing with.

Symptoms of Cow's Milk Allergy in Babies

Symptoms of rapid onset of allergy include:

  • Anaphylaxis
  • Coughing or difficulty breathing
  • Hives and rashes
  • Swelling lips, tongue, or throat
  • Vomiting
  • Wheezing breathing

Symptoms of slow onset of allergy include:

  • Abdominal pain
  • Colic
  • Diarrhea
  • Rectal bleeding

Anaphylaxis, though rare in infants, requires immediate medical attention. Signs can include:

  • Difficulty breathing
  • Swollen lips, tongue, throat, face
  • Red, flushed appearance
  • Itching

If your baby's symptoms lead you to suspect a cow's milk allergy, visit a pediatrician or a pediatric gastroenterologist. They will likely perform a Hemoccult test, which looks for traces of blood in your baby's poop. A cow's milk allergy can cause inflammation of the intestines, often leading to small amounts of blood.

mother and baby buying cheese in grocery store
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What to Do for a Baby's Milk Allergy

You can still breastfeed or chestfeed your baby even if you suspect that they have a cow's milk allergy. But to avoid passing on the proteins that trigger the allergy through your breast milk, you must eliminate cow's milk and dairy foods like ice cream, cheese, and yogurt from your diet.

Your baby's symptoms should improve once the cow’s milk completely clears from your system and your baby's system in three to four weeks. If their condition doesn’t improve, consult your pediatrician. They might advise eliminating other common allergens (like soy, wheat, peanuts, and eggs) from your diet and see if that helps.

Even if your baby's symptoms persist, most doctors agree that there's still no reason to stop nursing since the benefits far outweigh a little intestinal inflammation in an otherwise healthy baby. After your baby recovers, your doctor may recommend slowly reintroducing cow's milk into your diet (unless your infant has a severe allergy). Simply stop again if the symptoms return.

Some good news: Your baby likely won't be allergic to cow's milk forever; many kids outgrow it by age 6. According to research, 50% of babies with a cow's milk allergy will develop a tolerance by age 1, 75% of babies will develop a tolerance by age 3, and 90% will develop a tolerance by age 6.

Cow milk allergies are also different from lactose intolerance (which is an inability to digest the natural sugar in milk), which usually shows up in older children or adults.

Can Babies Be Allergic to Breast Milk?

Some parents may wonder if babies can be allergic to breast milk itself. According to Petersen, the general answer is no. "There are some extremely rare medical conditions that could cause a breast milk allergy, but it happens so infrequently that this isn’t something [parents] should worry about," Petersen says.

Allergy to breast milk is rare. According to the American Academy of Pediatrics, only 2–3% of exclusively breastfed babies will show signs of allergy. Even then, most of those rare cases turn out to be an allergy to foods the nursing parent had ingested, not the breast milk itself.

If you have concerns about your baby's health, including food allergies, talk to your child's pediatrician.

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  1. Cow Milk Allergy. StatPearls. 2022.

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