What Is Milk Protein Allergy and How Is It Treated?

Whether they are formula-fed or breastfed, many infants are diagnosed with milk protein allergy. Also known as cow’s milk allergy, this condition confuses many parents. As many as 2-5% of infants have this problem in the first year of life, so it affects a lot of babies. It is important to recognize the symptoms of milk protein allergy so it can be treated effectively.

What Is Milk Protein Allergy?

It’s best to start with what milk protein allergy is not: despite its name, for most infants, it is not an actual allergy. Most food allergies, like those to peanuts or shellfish, activate a part of the immune system that can lead to anaphylaxis, or a dangerous cascade of reactions that can lead to such serious consequences as swollen lips or tongue, constricted airway, difficulty breathing, and a drop in blood pressure. At its worst, anaphylaxis can lead to death.

But a milk protein allergy usually is not a true allergy and so does not lead to these problems. This condition is more accurately described as a milk protein intolerance, rather than an allergy. In fact, the condition is sometimes referred to as “food protein-induced proctocolitis.” That is, it is an inflammatory process in the furthest part of the colon triggered by food. Milk is just one food that triggers this process, but others are soy, egg, and corn.

What Are the Symptoms of Milk Protein Allergy?

Most infants with milk protein allergy will have symptoms from minutes to two hours after drinking a milk-based formula, but most severe symptoms will occur within the first 30 minutes after eating.

It is important to know that symptoms can be variable, but can include:

  • Abdominal pain or discomfort
  • Diarrhea
  • Constipation
  • Vomiting
  • Rectal bleeding
  • Mucus in the stool
  • Rashes

The abdominal pain or discomfort may be interpreted as “colic” by some parents, partly because milk protein allergy usually presents between 2 to 8 weeks of age, and colic is common after 6 weeks of age. But colic is not related to feedings, and does not manifest with the other symptoms mentioned above.

Less common symptoms include eczema and respiratory symptoms, such as nasal congestion, runny nose, and coughing. In the rare case that milk triggers a true allergic reaction, symptoms can include hives, wheezing, and difficulty breathing.

And remember that these symptoms can appear even in breastfed babies if the mother’s diet includes milk or other dairy products.

What is the Treatment for Milk Protein Allergy?

The mainstay of treatment is to eliminate the culprit food from the infant’s diet, whether it be milk, soy, or other food. For breastfed babies, that means the mother must eliminate milk, dairy, soy, or whatever food or foods are found to be the cause of the problem.

For formula-fed babies, that means stopping the milk-based or soy-based formula and using a hydrolyzed formula (also known as a hydrolysate). These formulas have the proteins cut up into much smaller pieces, which are therefore less likely to cause problems. These formulas come as either partially hydrolyzed or extensively hydrolyzed. The American Academy of Pediatrics recommends using only extensively hydrolyzed formulas for the treatment of milk protein allergy, two of which are Nutramigen and Alimentum. Symptoms should resolve on these formulas after a few days to two weeks.

If symptoms persist on these formulas, the next step is using a formula made of only amino acids, the building blocks of proteins. These formulas are more expensive and have some minor side effects, so should only be used at the direction of a medical professional. Examples of these formulas are Pregestimil, Elecare, or PurAmino.

For most babies, the milk protein allergy will resolve on its own by 12 months. So at 12 months, most infants with milk protein allergy will transition to cow’s milk (usually whole milk) without a problem. If symptoms persist, the child is placed back on the tolerated formula, and transitioned again at a later date, such as 15 months.

There is no true preventive measures that you can take to avoid milk protein allergy in your infant. Obviously, breastfeeding is usually the best option for infants, but when the mother is unable to breastfeed or chooses not to, then regular formula is a good option. But there is no conclusive evidence that starting infants immediately on the hydrolysate formulas will prevent milk protein allergy or any other food allergies.

Ruben Rucoba
Dr. Rucoba has over 25 years of experience as a primary care pediatrician after completing medical school at the University of California, San Francisco. His clinical areas of expertise include caring for children with special health care needs and assisting families with international adoption. He has been a freelance medical writer since 2010, writing for health websites, continuing medical education providers, and various print outlets. He currently works at Wheaton Pediatrics in the suburbs of Chicago, where he lives with his wife and four daughters, including a set of twins.

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