How To Recognize a Milk Allergy in Your Baby

Food allergies in babies can feel overwhelming, especially when symptoms affect feeding, sleep, digestion, or your baby’s comfort. Milk allergy is one of the most common food allergies in infancy, and symptoms can range from mild digestive issues to more serious allergic reactions.¹

Before I had children of my own, I worked in a pediatric food allergy clinic. Later, both of my daughters were diagnosed with milk allergies as infants. Because of my experience, I recognized the signs early and understood how to adjust my diet while breastfeeding. Here’s what parents should know about milk allergy symptoms, diagnosis, treatment options, and how milk allergy differs from lactose intolerance.

What Is a Milk Allergy?

A milk allergy occurs when the body reacts poorly to exposure to cow’s milk or milk from other mammals, such as sheep, goats, or buffalo.¹ The technical term for a milk allergy is cow’s milk protein allergy (CMPA).⁷ Most reactions happen after eating or drinking milk, but in rare cases, breathing in milk particles or touching milk products can also cause an allergic reaction.²

Related: Baby Reflux: What It Is and How To Treat It

Types of Milk Allergies and Their Symptoms

There are different types of milk allergies, caused by distinct immune cell reactions and body systems. Symptoms of milk allergy can vary depending on the type of allergy.¹ Milk allergies can affect babies differently depending on how the immune system responds to milk proteins. Here are two types of true milk allergies classified by the type of immune response causing the reaction:

1. IgE-Mediated Milk Allergy

One type of milk allergy is an IgE-mediated reaction, named for the type of immune response. IgE-mediated allergies typically cause more immediate reactions after consuming milk. This type can cause anaphylaxis, a serious reaction characterized by symptoms such as throat swelling and breathing difficulties.² An IgE-mediated milk allergy can affect the skin, gut, and/or respiratory systems. Symptoms of milk allergy include:³

• Rash, itching, hives, and swelling
• Nausea, vomiting, diarrhea, and abdominal pain
• Sneezing, congestion, itchy or runny nose, coughing, wheezing, and shortness of breath

2. Non-IgE-Mediated Milk Allergy

There’s also another type that isn’t mediated by IgE antibodies. This non-IgE-mediated milk allergy involves a different part of the immune system that reacts when exposed to milk. Like IgE-mediated allergies, non-IgE-mediated milk allergies can also affect the skin and gut. Symptoms include:

• itching and eczema
• abdominal pain
• colic
• mucus or blood in the stool.³

While symptoms of both types can be similar, non-IgE-mediated milk allergies typically cause a delayed reaction up to 48 hours after milk consumption and don’t cause respiratory symptoms or anaphylaxis.³

Related: 12 Types of Baby Poop and What They Mean

Milk Allergy vs. Lactose Intolerance

In addition to the two types of milk allergy discussed above, there’s a third type of reaction called lactose intolerance. People often confuse milk allergies with lactose intolerance, but they’re different reactions to milk.³

While a true milk allergy is an adverse immune system reaction to the casein and whey proteins in milk, lactose intolerance is not an immune reaction. It’s a localized reaction in the intestines to the sugar (lactose) in milk.

Lactose is a large sugar molecule present in all mammalian milk, meaning that even breast milk has lactose.³ An enzyme in the gut called lactase breaks down lactose into sugars that can be more easily digested and absorbed. The lactose in breast milk provides a significant amount of daily calories and energy to breastfed babies.⁴

Symptoms of lactose intolerance include bloating, gas, diarrhea, and abdominal pain.³ Lactose intolerance doesn’t appear in children under the age of 5, except temporarily. An illness or infection, such as a stomach virus, can temporarily reduce the amount of lactase in the intestines, causing short-term lactose intolerance. Once the child heals, their lactase will return, and they’ll be able to digest lactose again.⁴

Breastfed infants affected by temporary (or “secondary”) lactose intolerance should continue breastfeeding, and formula-fed infants can try a lactose-free formula temporarily.⁴ The lactase enzyme naturally and gradually declines as children age and wean from breast milk, causing gastrointestinal symptoms with significant milk consumption in older children, teens, and young adults.⁴

What Causes a Milk Allergy?

While decreased lactase activity in the intestines causes lactose intolerance, a true milk allergy occurs when the immune system mistakenly identifies milk protein as a threat. It attacks the milk protein with histamine, a chemical that triggers typical allergic symptoms such as itching, sneezing, and diarrhea.¹

There’s also a genetic component to this allergy. According to one study, infants with a milk allergy were much more likely to have first-degree relatives with other atopic conditions such as eczema, asthma, and allergy.⁵ Anecdotally, both of my daughters had a non-IgE-mediated milk allergy, and my husband has asthma and other environmental allergies. I highly doubt that’s a pure coincidence!

How Is a Milk Allergy Diagnosed?

Many milk allergy symptoms can overlap with other common infant issues, which is why proper evaluation is important.

Diagnosing a milk allergy may involve a combination of symptoms, testing, and dietary changes. The diagnostic process may vary depending on your child’s symptoms and the type of milk allergy you suspect. If the cause of an allergic reaction is unclear or you or your doctor suspect a milk allergy in your baby based on skin, tummy, or breathing symptoms, they’ll likely want to perform some tests. They can diagnose IgE-mediated allergies (remember, these are the immediate-reaction allergies with skin, respiratory, and stomach symptoms) with the following:^3,6

Skin Prick Test

When I was a food allergy nurse, I performed skin prick tests on patients in our clinic. A small amount of milk protein is scratched onto the surface of the skin, usually on the back of a small baby, or on the forearm of a larger baby or child. After letting it sit for 15 minutes, we observe and measure the skin reaction to the milk protein. If it looks like a large hive or a bug bite, this may indicate a milk allergy.

Blood Test

Your baby’s blood can also be drawn and analyzed for the presence of IgE (Immunoglobulin E) in milk. If the IgE is above a certain value, your baby is likely allergic to milk.

However, these cutoffs aren’t exact.³ The only definitive way to diagnose this allergy is through an oral food challenge.⁶

Oral Food Challenge

As a food allergy nurse, I used to administer oral food challenges under the supervision of doctors in a clinic or hospital. We would feed a child tiny, gradually increasing doses of milk while monitoring for signs and symptoms of an allergic reaction.

If no symptoms appeared, we would proceed to the next dose. If the child passed the challenge, they weren’t allergic to milk, and the doctor would provide instructions on safely introducing the food into their diet. And if allergic symptoms occurred, we would treat the reaction with an antihistamine or epinephrine and consider the child to be allergic.

Related: The Best Way to Expose Your Baby to Allergens

Diagnosing Non-IgE Mediated Milk Allergies

Oral food challenges can also be used to diagnose non-IgE-mediated milk allergies, but this is more difficult because the reactions are often delayed.⁶ Non-IgE milk allergies can be diagnosed anecdotally and by checking for blood in the stool.⁶

My daughters both had non-IgE-mediated milk allergies as infants. Each of their main symptoms was blood in their stool. I started to notice that if I consumed a large amount of dairy and then breastfed them, their symptoms got worse. Our pediatrician tested their diapers for blood, though I could see it without the test. These two factors, combined, led our pediatrician to suspect a milk allergy. I eliminated dairy from my diet and continued to breastfeed, and their symptoms resolved. This is an example of an exclusion diet.³

How Is a Milk Allergy Treated?

Many breastfed babies with milk allergies can continue breastfeeding successfully with dietary adjustments from the breastfeeding parent.

Treatment focuses on avoiding milk proteins while making sure your baby still receives proper nutrition. If your child has a milk allergy, the safest way to prevent an allergic reaction is to completely avoid consuming any type of milk or milk product. In addition to avoiding milk, you must be prepared if your child accidentally consumes milk. Finally, you need to determine what alternative formulas and diets will work for them. Let’s explore these treatment options further:

Avoidance

To avoid consuming milk or feeding it to your milk-allergic child, be sure to read all food labels for allergen statements that a product contains milk. Look for ingredients such as:¹

• Milk
• Cheese
• Butter
• Casein
• Whey
• Yogurt
• Cream

Preparedness

If your child receives a milk allergy diagnosis, the doctor will prescribe medications with instructions to administer them if your child accidentally consumes milk. If accidental ingestion happens, you should monitor for signs of a reaction and administer antihistamines, epinephrine, steroids, or anti-vomiting medications per your doctor’s orders. You should also go to the emergency room.⁷

If the mother of a milk-allergic baby is breastfeeding, she may also need to avoid all sources of milk in her diet, as these proteins can sometimes pass through the breastmilk to her allergic infant.⁶ I went dairy-free for about the first nine months of each of my daughters’ lives because they were allergic to milk and I was breastfeeding.

If your formula-fed baby needs to avoid milk, there are different types of hypoallergenic or dairy-free formulas:

Hydrolyzed Formula

In a hydrolyzed formula, the milk proteins casein and whey are broken down extensively and typically don’t cause a reaction. Most infants who are allergic to milk can tolerate hydrolyzed formula.^1,3

Amino Acid Formula

If your baby is still having allergic reactions to hydrolyzed formula, your doctor may recommend trying an elemental or amino acid-based formula. This is one in which the proteins are completely broken down and no longer recognizable as milk proteins. Amino acid formulas should be a “last resort” if your baby isn’t tolerating extensively hydrolyzed formula.³

Soy Formula

Soy formula is also available, and some people wonder whether it can be used as a substitute for milk-based formulas. Babies under 6 months typically shouldn’t have it because it has similar effects to estrogen. Also, many babies who are allergic to milk are also allergic to soy.³

This was true for my girls — in addition to avoiding all dairy, we avoided all soy, including edamame, tofu, miso, soy lecithin, and more. Soy formula must also be fortified to be nutritionally complete for an infant.¹

Regular follow-up with your pediatrician or allergist can help monitor symptoms and determine when it may be safe to reintroduce milk.

Can a Baby Outgrow a Milk Allergy?

It can be overwhelming to receive this diagnosis and have to overhaul your or your child’s diet completely. Fortunately, many children eventually outgrow this allergy during childhood.^1,2 But until a child has outgrown their milk allergy, they should avoid consuming milk completely. A baby with a diagnosed milk allergy should avoid milk entirely for at least six months. After that time (depending on lab values, symptoms, and other factors), your doctor may consider gradually reintroducing milk into your diet.³

Some new therapies are under investigation to help children outgrow their milk allergies. Oral immunotherapy involves feeding a child a tiny amount of milk daily and gradually increasing the dose. This isn’t FDA-approved and is currently only done in research studies under the close supervision of a medical team.⁷

Sometimes a child can tolerate milk when it’s baked into foods such as muffins, even if they can’t eat or drink milk directly. Your doctor may recommend a supervised food challenge with baked milk to see if your baby can tolerate heated milk before gradually increasing the volume and decreasing the degree of baking.3 The theory is that these small exposures to milk over time help desensitize your child’s immune system to milk and help them outgrow their allergy. However, you should only do this with your pediatrician or allergist’s help. It’s also important to note that these therapies require keeping milk in the diet regularly — you can’t stop feeding your child milk for a while and then pick up where you left off.⁷

Living With a Milk Allergy in Babies

A suspected or confirmed milk allergy in your baby can feel stressful at first, especially when feeding and comfort become daily concerns. Fortunately, many babies improve significantly once milk proteins are removed from their diet, and many children eventually outgrow their allergy over time. Working closely with your pediatrician or allergist can help you safely navigate feeding choices and treatment options for your child.