Baby bottle and breast pump

Cow’s Milk Allergy

Understand more about this common food allergy in infants and children.

Cow’s milk allergy (CMA) is one of the most common food allergies in infancy and early childhood. It is a hypersensitivity reaction to one or more bovine proteins found in cow milk and dairy products. 

When a baby is allergic to cow’s milk, their immune system, which normally fights infections, overreacts to one or more bovine proteins in milk. As a result, every time the baby drinks milk or eats dairy products, the body thinks these proteins are harmful invaders this causes them to have a reaction.

CMA is sometimes confused with lactose intolerance. Both can cause problems after drinking milk or eating dairy products, but they are very different and unrelated.

CMA is a reaction to the PROTEIN in milk, while lactose intolerance is a reaction to the SUGAR (lactose) in milk. Therefore, lactose-free milk would not be helpful for a baby with suspected CMA. Of note, lactose intolerance is typically not found in babies.

Are there different types of cow milk allergy?

Yes. Cow milk allergy can be IgE mediated, non-IgE mediated or a mix of both. 

IgE allergies are the classic allergies we think of when babies get hives/rashes and experience difficulty breathing after eating something. This allergy can be tested for with skin prick testing (and blood tests). These allergies are the ones that might need an epinephrine pen, steroid medicines, or Benadryl to manage. Reactions occur within minutes (or up to 2 hours) after drinking cow’s milk. 

Non-IgE mediated cow milk allergy, on the other hand, is not driven by IgE but is considered a delayed hypersensitivity reaction. There is no risk of associated breathing problems or anaphylaxis with this type of allergy; however, many babies experience vomiting and/or blood/mucus in the stool. It is called a delayed hypersensitivity reaction because the symptoms don’t occur immediately but can take up to 48 hours (or even up to a week). The remainder of the talk will be about the non-IgE mediated cow milk allergy (also shortened to CMA).

What causes CMA?

Unfortunately, the cause of CMA is not known. We do know it is an immune system response to specific proteins (predominantly cow’s milk). CMA is much more common if there is a family history of asthma/allergies/eczema (also known as atopy). Up to 25% of babies with CMA have a family history of atopy (immune system is more prone to develop allergic reactions or triggers), and half of babies with CMA will themselves also have eczema.

What are the symptoms of early childhood cow’s milk allergy?

While CMA symptoms can be scary and cause alarm, once the cow milk is removed from the diet, babies otherwise continue to grow and thrive; they gain weight and continue to reach their developmental milestones. If the baby does not look well, is losing weight, looking pale or lethargic, becoming dehydrated, something else could be going on. The baby might need further assessment by a physician and other investigations.

CMA can present as early as a week old and generally first occur within the first six months of life. However, in most babies it will resolve by one year of age. 

The classic CMA presentation is blood in the poop. It can be associated with increased frequency of poops, looser consistency of poops and/or mucus in the poop. The blood is generally flecks or streaks. The blood is mixed with the poops and is a red colour (rather than maroon or brown). The other common cause of blood in the poop at this age is constipation, with small tears at the anus from hard poop. However, with CMA, the poop is most often soft or looser rather than hard.

Some babies present with symptoms of reflux/regurgitation. This includes spit up and sometimes vomiting. They may also have feeding refusal (or a change in their feeding). In addition, some babies may experience increased gas, pain when pooping (i.e. constipation), and experience abdominal pain (i.e. colic). 

How is a Baby Diagnosed with a Cow’s Milk Allergy?

A doctor diagnoses CMA based on presenting symptoms, the age of the baby and the lack of any red flag symptoms that would suggest an alternative diagnosis. 

Tests and procedures used to diagnose Cow’s Milk Allergy

If the doctor suspects CMA, your baby will likely need to take the oral food challenge (OFC). An OFC involves strictly removing cow’s milk from the diet, also known as an elimination diet, for two weeks and watching for improvement of symptoms. If the baby is formula-fed, using a hydrolyzed or an extensively hydrolyzed or amino acid formula is important. If symptoms improve (and ideally resolve), the next step of the OFC is to reintroduce cow’s milk protein and observe for a recurrence of symptoms. If the previous symptoms recur, this confirms a CMA diagnosis. 

Once the baby’s symptoms have improved (and resolved), parents may choose not to reintroduce cow’s milk. It is important to not experiment by yourself. Please do not experiment with an elimination diet before consulting with a healthcare provider.

Breastfed Infants

In breastfed babies, moms can continue to breastfeed their babies even with a CMA diagnosis. However, to manage symptoms, we recommend moms remove dairy from their diets. Diets need to be strictly dairy-free and followed for a minimum of 2 weeks. 

There is a 10-15% chance babies will respond to soy proteins similar to that of milk proteins (called co-reactivity); therefore, soy can be removed from the diet too. Symptoms of reflux/regurgitation should start to improve within 3-5 days; however, blood in the stool and loose stools can take up to 2 weeks to start to improve. 

If at two weeks, symptoms have not improved, consider following up with your doctor or paediatrician and address the following:

  1. Are there hidden sources of dairy that have not been removed? Consider a dietitian appointment to discuss mom’s diet.
  2. Has mom waited long enough with the strict changes? A minimum of 2 weeks is needed.
  3. Is there an ongoing slimy appearance in the poop? If the blood has resolved and the poop is more formed, that indicates that things are improving. Slimy appearance of the poop occurs more with the extensively hydrolyzed infant formula (than for breastfed babies). But in either case, diarrhea and blood should have improved.

If symptoms are still not improving, there are two additional options to consider:

  1. If mom wants to continue breastfeeding, it is recommended she consult with her healthcare. Up to 20% of babies c may react to more than just one food. 
  2. If mom decides to stop breastfeeding at this point, she can proceed with a formula-fed method.

Formula-Fed infants

If bottle-fed using a traditional formula, baby will need to change to a hypoallergenic extensively hydrolyzed formula.

This type of formula has the cow’s milk protein broken down so the baby’s immune system won’t react to the protein. The two extensively hydrolyzed formulas available in Canada are Alimentum and Nutramigen. 

Many other formulas will say ‘broken down proteins’ or ‘partially hydrolyzed’ on them, but these proteins are not broken down enough to prevent a reaction. Unfortunately, extensively hydrolyzed formula is more expensive than regular formulas. However, there are different ways to get this covered if it is sole-source nutrition. You can speak to your doctor or paediatrician to learn more. 

When changing to an extensively hydrolyzed formula, the formula must be given to the baby exclusively for a minimum of two weeks. Symptoms of reflux/regurgitation should start to improve within 3-5 days; however, blood in the stool and loose stools can take up to 2 weeks to improve. 

If in two weeks symptoms have not improved, it is recommended you follow up with your doctor or paediatrician. They will review symptoms to determine if the blood and diarrhea have improved/resolved. If there has been little to no improvement on the extensively hydrolyzed formula, the next step would be to proceed to an amino acid-based formula. These formulas do not have any bovine protein and are made entirely of free amino acids.

The two amino acid-based formulas available in Canada are Neocate and Puramino. This type of formula should be trialled for a minimum of two weeks while observing for improvement and resolution of symptoms. Up to 10% of infants will require an amino acid-based formula. 

Soy Formula 

Soy formula can be used in babies six months and older who have CMA, assuming the baby doesn’t fall into the small percentage who have a co-reactivity to soy. 

Soy can be given to babies six months and older if there is a concern about the taste of the extensively hydrolyzed formula or concern about the cost of the extensively hydrolyzed formula. 

Luckily most provinces cover the cost of the formula through provincial health plans, as it is considered almost like medicine when it is a baby’s sole source of nutrition. 

There is a potential risk of negative effects from the phytoestrogens in soy formula in babies less than six months old. As the volume of formula consumed in a day is high, the amount of phytoestrogens is equally high, creating negative effects. However, after six months of age, the risk reduces with the introduction of solids and the volume of formula needed decreases. 

Breastfed and formula-fed infants (mixed diet)

If baby is taking both breast milk and formula, a few diet changes will be needed. First, cow’s milk should be strictly removed from mom’s diet. As well, changing to a hypoallergenic extensively hydrolyzed or amino acid formula should be explored. 

Scan food labels

For breastfeeding moms, once you remove milk protein, it is important to follow a strict dairy-free diet. Reading food packaging labels will help ensure you avoid eating food products that contain milk protein.

Will my baby require a special diet?

Babies generally don’t outgrow this condition until closer to 1 year of age. As such, when solids are introduced (between 4-6 months), parents/caregivers should avoid giving the baby any products with dairy (yogurt, cheese etc.) until the CMA has resolved. 

Will my baby require vitamin or mineral supplements?

If a baby does not outgrow CMA by one year of age, it’s worthwhile scheduling a visit to see a dietitian to ensure the baby has a nutritionally complete diet. It’s possible that without dairy in the diet, baby may be missing specific vitamins/minerals, such as calcium. A dietitian can review the baby’s diet and determine if any supplementation is needed. The goal is to modify the diet to incorporate the missing vitamins/minerals through food sources; supplements can be challenging to take at an early age.

How can I avoid a reaction outside of the home?

Usually, this condition resolves by the age of one. However, if a baby is in daycare before CMA has resolved, the teachers/childcare providers should be aware of CMA and keep the baby’s diet dairy-free. 

Is this a life-long allergy?

Babies and young children outgrow CMA, usually by the time they turn one. 99% of CMA are resolved by six years old. Introducing dairy back into the diet typically happens around 9-12 months of age. If symptoms recur at that time, dairy should be removed again. Dairy can be reintroduced every three months thereafter until tolerated. Always consult your doctor or dietitian before reintroducing dairy in your child’s diet.  

Will my baby be able to meet all their developmental milestones?

Yes. Having CMA does not impact a baby’s ability to reach developmental milestones. Once cow milk protein is removed from the diet, and the baby is getting good nutrition (and good hydration), they will grow and meet their milestones. 

Can my baby develop health complications because of CMA?

Most babies with CMA are otherwise healthy. Even before a CMA diagnosis, depending on the severity of the reaction, they usually continue to grow well.

Having CMA alone does not significantly increase the risk of developing classic (IgE) allergies later in life. Approximately 4% of children will develop classic allergies later on, as is more commonly seen in children with CMA and eczema/atopy. However, children may be able to outgrow these classic allergies as well.

Who do I see if I suspect a cow’s milk allergy?

If you suspect a CMA, consult with your family doctor or paediatrician. Either healthcare provider can confirm, rule out and give you advice on a CMA.

It’s helpful to take pictures of the baby’s poop when you see blood and show these to your baby’s family doctor or paediatrician. If your baby is not doing well (pale, lethargic, dehydrated, febrile, etc.), please go to the emergency department for care. 

Should I keep a food diary?

If you are breastfeeding and see blood in the baby’s poop (or other symptoms of CMA), you can record what YOU ate in the last 48 hours leading up to the event. If there has not been a diagnosis made yet, it will help identify the culprit proteins. If your baby has received a diagnosis and a symptom recurs, a food diary will help determine if the problem was accidentally eating dairy protein or if a new food protein is causing symptoms.

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