Breastfeeding When Your Baby Has a Milk Allergy

Milk allergy, also called dairy allergy, cow's milk protein allergy (CMPA), or cow's milk allergy (CMA), is the most common food allergy in kids. Many breastfeeding parents worry that eating dairy may cause sensitivities and allergic reactions in their babies. However, this is not usually the case as dairy allergy is relatively uncommon in babies, with an incidence estimated to be well below 1%.

While it's true that much of the food that you eat does travel into your breast milk, you don't need to eat dairy-free unless your baby has a diagnosed milk protein allergy and your doctor advises you to abstain. In fact, even if your baby does have a milk allergy, you may not need to skip eating dairy.

Essentially, most babies will not react to any of the foods in their mother's diet, occasionally, some will. When a child does have a reaction to something in breast milk, the culprit may be cow's milk. However, as noted above, some researchers stipulate that even in cases of dairy allergy, most often, not enough of the milk protein passes into the milk to cause a reaction.

What Is a Milk Protein Allergy?

A milk protein allergy involves an immune response to ingesting milk protein. This response usually occurs right away after ingestion. A dairy intolerance or sensitivity differs from a true allergy in that an allergy triggers the immune system as well as digestive issues, while sensitivity to milk/dairy only causes digestive problems or discomfort.

Note that a cow's milk allergy is not the same as lactose intolerance. A baby with an allergy to cow's milk is reacting to the protein in dairy. Lactose is a type of sugar, not a protein. It's very unusual for a newborn or infant to be sensitive to lactose—an issue that is typically seen in adults or older children. For this reason, if your baby does have a milk allergy, lactose-free dairy products will still cause a reaction.

Symptoms of Dairy Allergy in Breastfed Babies

The most common symptoms of a cow's milk allergy in a breastfed baby are stomach-related and may include bloody stool. Signs and symptoms of dairy allergy in breastfed babies may include the following:

• Colic
• Constipation
• Diarrhea (including bloody diarrhea)
• Eczema
• Fussiness
• Irritability
• Red, itchy rash
• Runny or stuffy nose
• Stomachache
• Swelling of the lips and face
• Vomiting
• Wheezing

When speaking with your healthcare provider, be as detailed as possible when you're describing what's going on with your baby. Keeping a food diary with the timing of symptoms can be helpful. The more information the doctor has (such as whether there is a family history of food allergies), the easier it will be to narrow down the cause of your baby's discomfort.

Dairy Allergy and Formula

If your baby breastfeeds and takes formula, a cow's milk-based formula can cause milk allergy symptoms. Milk allergy is actually more prevalent (and often more severe) in formula-fed babies. If formula is the cause, you may need to change the brand you use. Soy formula is an option, but it can also cause allergies in about 10% to 15% of infants who are allergic to the cow's milk protein. A hypoallergenic formula may be used instead.

Identifying Infant Milk Allergy

Be sure to have your child evaluated by their pediatrician and/or an allergy specialist to ensure your child actually has a milk protein allergy. This is especially important because while 1% of babies have a true milk allergy, upwards of 14% of parents falsely assume their babies have this issue.

According to researchers in a 2020 study, "Clinical trials do not provide consistent support for using maternal or infant cow’s milk exclusion to manage common symptoms in infants without proven CMA. We estimated that for more than 99% of infants with proven CMA, the breastmilk of a cow’s milk–consuming woman contains insufficient milk allergen to trigger an allergic reaction."

So, don't stop breastfeeding because of a suspected or confirmed allergy to cow's milk protein, unless instructed to do so by your doctor. In fact, as mentioned above, even if your baby does have a milk allergy, you can usually still consume dairy and (almost always) continue breastfeeding.

Doctors may do a variety of tests to look for milk allergy, including a skin prick test or blood test. However, the most common way to test for a milk allergy in an exclusively breastfed baby is to eliminate cow's milk from the maternal diet, along with common dairy foods like cheese, yogurt, and butter, to see if that makes a difference in your child's symptoms.

If, after two weeks of a dairy-free diet, you do not see any difference and your child is still showing signs of an allergy, then dairy is probably not the cause of your baby's issues. Another allergen, or another medical condition, may be the problem. But if you do see improvement, then do your best to stay on the dairy-free diet as long as recommended by your doctor.

Treatment With a Dairy-Free Breastfeeding Diet

If you do need to eliminate dairy, there are many substitutes for cow's milk and milk products available. Just look for dairy-free on the labels at the grocery store. Since milk is a known allergen, it must be identified on food labels. Remember that milk can be found in many different products, including soups, salad dressing, and baked goods.

Keep in mind that even though a reaction to cow's milk is the more common one, soy and nuts can also cause allergies in breastfed babies. Also, you'll need to be careful that you consume enough calcium from non-dairy sources in order to meet your (and your baby's) nutritional needs.

Will Your Baby Outgrow an Allergy?

Even if your doctor recommends you eliminate dairy, you don't necessarily have to stay away from dairy for as long as you breastfeed. Once you've eliminated all the dairy and your child is feeling better, under the direct supervision of your doctor, you can wait a few weeks or months, then slowly reintroduce some dairy products back into your diet.

If your baby starts to react, you can stop the dairy once again. With your doctor's go-ahead, you can keep trying to add back dairy every few weeks or so, and as your baby gets older, they may be able to tolerate it more and more, as it's quite common for children to grow out of their milk allergy. 

A Word From Verywell

It's understandably worrisome if you think your baby could be reacting negatively to something in your breast milk. However, most often, even if they do have a cow's milk allergy, breastfeeding is still best for your baby. It can be exhausting and difficult to care for a child who cries frequently and appears to be in pain and elimination diets are often quite challenging—so be sure to get an accurate diagnosis to be sure you are treating the right issue.

Talk to your partner, your doctor, and/or your baby's doctor to get all the information and support you need to make the appropriate treatment plan for you and your baby. Sometimes, you may decide to wean your baby. Alternatively, you may decide to keep breastfeeding while sticking to a dairy-free diet or continue nursing without changing your diet. Whatever option you and your doctor decide is the best way to feed your baby—and you—is the right choice for your family.