top of page

Can My Breast-Fed Baby Really Be Allergic to My Milk?

“I was told my baby is intolerant to lactose, so now I give a lactase supplement.” This is a common topic discussed on consults with our experts. You want to know if your baby is allergic to your breast milk or lactose intolerant, right? First, there is a big difference between lactose intolerance and an allergic reaction caused by food allergens.

Let’s dig into the science because you know that’s what we’re about!

What Does Lactose Intolerance Really Mean?

Lactose intolerance is the inability to properly digest the sugar found in milk. This specific sugar is known as lactose, due to inadequate levels of the digestive enzyme lactase.

Lactose can be found in all mammalian milk and human milk contains even higher amounts than cow’s milk (ever taste your breast milk? It’s sweet!). [1] Those who suffer from low lactase levels will experience digestive issues after consuming milk products.

What Is a Lactase Enzyme Supplement?

Products that claim to be lactose-free are those made of regular milk which has an extra lactase enzyme added to “digest” the lactose for you. This enzyme breaks lactose down into its smaller components, glucose, and galactose, for absorption. [3]

Similarly, over-the-counter supplements are available that contain the same enzyme to allow those with low levels to still properly digest lactose. These can be found in various concentrations depending on the target audience.

Do Babies Ever Really Have Lactose Intolerance?

Infant lactose intolerance is INCREDIBLY rare. All babies are born with lactase in their intestines. As they grow into adolescents and adults the levels may decrease, eventually leading to intolerance. That’s why you’ll notice way more adults or older people talking about lactose intolerance.

About the only two scenarios that a baby has this is:

(1) Premature babies may have a short period of developmental lactase deficiency or infants with severe bowel injury (such as a virus).


(2) Congenital lactase deficiency at birth. Not only rare but also easy to spot because symptoms of lactose intolerance in infants include diarrhea to the point of severe dehydration and weight loss immediately after birth .[4]

If your baby does not fit into one of those two categories, they do not need a lactase supplement!

Double-blind medical crossover trials show no difference between treatment and placebo in breath hydrogen (a method of testing for the intolerance) and mean duration of crying. [5-6]

A handful of studies possibly linking enzymes to reduced colic have been funded by formula and lactase enzyme companies .[7-9]

Read that last sentence again. Funded by formula companies…Doesn’t that seem strange to you?

Even with the best of intentions, this is adding an unnecessary increase in a digestive enzyme of which babies have an abundance. Unfortunately, this can cause adverse effects for some infants, such as diarrhea, and leave parents all the more confused.

What Could Possibly Be Wrong With My Baby While Breastfeeding?

A milk allergy is caused by a reaction to the protein in cow’s milk and is the most common infant food intolerance. [10] When ingested by a lactating parent, this protein can potentially enter her milk and cause a reaction in her infant. [11]

Research shows that after cow's milk ingestion some people have well over a dozen different types and portions of cow's milk proteins such as beta-lactoglobulin and casein. Lactase enzyme will not help to break down these proteins for baby or parent. So it simply doesn’t make sense to add a supplement when it’s not needed.

What’s Important to Remember When Trying To Find Answers On Your Baby

There have literally been only a few babies in the world with true human milk intolerance. Adverse reactions are immensely more likely to be due to a protein intolerance or allergy from dietary foods transferred to your milk. This is great news because this is a much easier fix than being told your baby is allergic to your breast milk or that your breast milk “is killing your baby” like Dr. Trill was told.

If you are avoiding dairy, don’t use products that are only “Lactose-Free” as they still contain milk protein. Instead, opt for dairy-free alternatives such as coconut-based products.

Similarly, if you are taking a prescription medication that contains Anhydrous Lactose (found in many birth control pills) it is likely safe to take while nursing a little with cow’s milk protein allergy. Check with your medical provider and pharmacy specifically for cow’s milk protein and not lactose or lactase.

If you're struggling to determine your little one’s triggers, schedule a one-on-one consultation today with one of our food allergy experts!


  1. Fusch, Gerhard, et al. "Quantification of lactose content in human and cow's milk using UPLC–tandem mass spectrometry." Journal of Chromatography B 879.31 (2011): 3759-3762.

  2. Swagerty Jr, Daniel L., Anne Walling, and Robert M. Klein. "Lactose intolerance." American family physician 65.9 (2002): 1845.

  3. Swallow, Dallas M. "Genetics of lactase persistence and lactose intolerance." Annual review of genetics 37.1 (2003): 197-219.

  4. Heyman, Melvin B. "Lactose intolerance in infants, children, and adolescents." Pediatrics 118.3 (2006): 1279-1286.

  5. Lankan, John B., et al. "Lactose-free milk protein-based infant formula: impact on growth and gastrointestinal tolerance in infants." Clinical Pediatrics 50.4 (2011): 330-337.

  6. Miller, John J., et al. "Effect of yeast lactase enzyme on" colic" in infants fed human milk." Journal of Pediatrics 117.2, I (1990): 261-263.

  7. Kanabar, D., M. Randhawa, and P. Clayton. "Improvement of symptoms in infant colic following reduction of lactose load with lactase." Journal of Human Nutrition and Dietetics 14.5 (2001): 359-363.

  8. Ahmed, Mubashir, et al. "Clinical Efficacy Of Lactase Enzyme Supplement In Infant Colic: A Randomised Controlled Trial." J. Pak. Med. Assoc 68 (2018): 1744-1747.

  9. Kearney, P. J., et al. "A trial of lactase in the management of infant colic." Journal of Human Nutrition and Dietetics 11 (1998): 281-286.

  10. Koletzko, S., et al. "Diagnostic approach and management of cow's-milk protein allergy in infants and children: ESPGHAN GI Committee practical guidelines." Journal of pediatric gastroenterology and nutrition 55.2 (2012): 221-229.

  11. Zhu, Jing, et al. "Discovery and quantification of nonhuman proteins in human milk." Journal of proteome research 18.1 (2018): 225-238.


bottom of page