Could My Infant Have Cows’ Milk Allergy?

Medically Reviewed by Dan Brennan, MD on December 08, 2022
6 min read

A cows’ milk allergy, also known as cows' milk protein allergy, can happen when cows' milk -- consumed by the mother of a breastfeeding baby or used in formula for bottle-feeding babies -- causes symptoms in the baby before being weaned, or if the baby consumes cows’ milk protein-containing products during or after weaning. The allergy usually appears in the first year of a baby's life, but most children will outgrow it.

Only 0.5% of exclusively breastfed babies are affected, and the symptoms are usually mild or moderate. This is one reason breastfeeding exclusively is recommended by experts for the first 4 to 6 months of a baby's life.

It is thought that infants who have a family history of allergy are more likely to have a cows’ milk protein allergy. The same goes for infants with eczema and asthma. Those with asthma can have severe reactions, especially if their lung disease is poorly controlled.

An allergy happens when the body's immune system mistakes a harmless substance -- in the case of food, a protein -- as a foreign invader and attacks it, much like it would attack bacteria or a virus. This abnormal response releases chemicals that in turn trigger the symptoms associated with an allergy.

Milk contains both casein (which forms the curd when milk goes sour) and whey (the watery part left when the curd is removed), and each of these has several different proteins, any of which can cause an allergic response.

A cows' milk protein allergy can cause different kinds of reactions, depending on the chemicals released, and the allergy is categorized based on these causes:

  • Immunoglobulin E (IgE)-mediated reactions: The immune system releases histamine and other chemicals in response to cows' milk protein. The symptoms usually occur within 20 to 30 minutes of consuming the protein, but they can appear up to 2 hours later.
  • Non-immunoglobulin E-mediated reactions: T cells are thought to be the trigger for the symptoms, which appear more gradually, from 48 hours up to a week after consuming cows' milk protein.
  • Mixed IgE and non-IgE reactions: This is a combination of immunoglobulin E-mediated reactions and non-immunoglobulin E-mediated reactions.

A cows’ milk allergy should not be confused with lactose intolerance, a condition in which the body cannot produce enough of the enzyme needed to digest a type of sugar found in milk.

A wide range of symptoms can be triggered by a cows' milk protein allergy, usually involving the skin, gastrointestinal tract, and respiratory tract. Those that involve the respiratory tract often appear along with other symptoms. These include:

IgE-mediated symptoms (these are acute and come on more quickly)

  • Skin reactions: Itchiness, reddening of the skin, sudden itchy rash (urticaria -- either in one spot or generally all over), or swelling, most often of the lips, face, and around the eyes
  • Gastrointestinal reactions: Swelling of the lips, tongue, or palate in the mouth, itchiness in the mouth, nausea, vomiting, colicky abdominal pain, or diarrhea
  • Respiratory reactions: Itchy nose, sneezing, runny nose, congestion, cough, wheezing, or shortness of breath

Non-IgE-mediated symptoms (these are non-acute and are delayed)

  • Skin reactions: Itchiness, reddening of the skin, or eczema
  • Gastrointestinal reactions: Acid reflux or gastro-esophageal reflux disease (GERD), loose or frequent stools (poo), blood or mucus in poo, abdominal pain, colic, constipation, refusing food or aversion to food, redness in the perianal area, tiredness
  • Respiratory reactions: Cough, wheezing, or shortness of breath

In rare cases, a child may have an anaphylactic reaction, which requires emergency medical help because it can be fatal. Call an ambulance if you think your infant is struggling to breathe or is floppy.

A cows' milk protein allergy can sometimes lead to complications due to malabsorption or poor nutritional intake. The child may get chronic iron deficiency anemia or fail to thrive.

If you suspect your infant might have a cows' milk protein allergy, make an appointment to see your pediatrician,  who will ask about the child's family history to find out if other members of the family have a food allergy, asthma, eczema, or allergic rhinitis. The doctor will want to know all about the symptoms and when they first appeared.

Before confirming a diagnosis of cows’ milk allergy, other conditions that may cause similar symptoms -- such as a food intolerance, other food allergies, Crohn's disease, celiac disease, and GERD -- may need to be ruled out.

If the doctor suspects an IgE-mediated cows' milk protein allergy, your infant will usually be referred to an allergy specialist for a skin prick test and/or an IgE antibody blood test. If confirmed, then strict avoidance of cows’ milk protein is needed.

For suspected non-IgE-mediated cows' milk protein allergy, the doctor may not need to refer your child to a specialist unless there are concerns about your child's growth or symptoms are acute or severe. Your doctor may recommend trying an elimination diet in which cows' milk protein is removed from the child's diet -- or the mother's if the infant is totally breastfed -- for a certain period of time, then reintroduced. If your baby has the allergy, their symptoms will go away during the elimination period then come back.

Beware of complementary or alternative health tests for food allergy, such as hair analysis or applied kinesiology. There’s no scientific evidence that they work, and an incorrect diagnosis of a food allergy or intolerance may lead to unnecessary dietary exclusions. Cutting out a large number of foods on the basis of these tests can lead to nutrient deficiencies that can mean your child may fail to thrive.

Most children will outgrow cows’ milk allergy.

Studies show that most children with non-IgE-mediated reactions will outgrow cows’ milk allergy by the time they are 3 years old.

For children with IgE-mediated reactions, studies show that about half of these children will outgrow cows’ milk allergy by the time they are 5 years old. Evidence suggests that a cows' milk protein allergy is more likely to persist in these children if they have asthma or allergic rhinitis, or if they have more severe reactions or higher milk-specific IgE antibody levels. Even so, it’s rare for adults to have a cows’ milk allergy.

If cows’ milk allergy is diagnosed, cows' milk protein will need to be eliminated from your child's diet.

For breastfeeding moms, that means you can’t have any dairy in your own diet. Cut out milk, butter, cheese, yogurt and ice cream, plus prepared foods that use dairy, like a lot of baked goods. Goats’ and sheeps’ milk have similar proteins to cows’ milk, so those products are off-limits too. Dairy can hide in processed foods under different chemical names, so check labels for:

  • Casein
  • Caseinates
  • Curd
  • Hydrolysed casein
  • Lactose
  • Lactoglobulin
  • Milk solids or milk sugar solids
  • Whey
  • Whey syrup sweetener

It’s hard to get enough calcium and vitamin D when you don’t eat dairy. Talk to your doctor about adding other calcium-rich foods to your diet, or taking a supplement.

If you’re bottle feeding, your doctor can recommend an allergy-free formula:

Extensively hydrolyzed formulas (eHFs): About 90% of infants with a cows' milk protein allergy can tolerate extensively hydrolyzed formulas. Although these are based on cows' milk, so the nutrient content is the same as normal infant formulas, they have been extensively broken down into tiny parts so that the child's immune system is less likely to recognize the protein.

Amino acid formulas (AAFs): If your child has trouble with a hydrolyzed formula, or has severe symptoms -- such as severe skin or gastrointestinal symptoms or has had an episode of anaphylaxis -- an amino acid formula may be recommended.

Don’t assume a soy-based formula will be safe. It can also cause a reaction in babies with a cows’ milk allergy. 

You will also be given advice on how to wean your child following a diet that excludes cows' milk. Because cows' milk provides a lot of important nutrients, especially calcium, a pediatric dietitian can help ensure that your child is getting enough of all the nutrients necessary for healthy growth.

You should be given a management plan that will not only include how to feed your child, but also treatment, such as antihistamines or creams in cases where a child has eczema. Follow-up appointments should continue to ensure your child is thriving.

Because children can outgrow cows’ milk allergy, your child should be reassessed as often as your doctor recommends, to determine if there is a change in tolerance of cows’ milk protein.