The Beauty of Breast Milk (and Its Ability to Keep Allergies at Bay)

by Lola Rosewig on March 6, 2013

Most people see the beauty of nature in pristine white sand beaches, the serenity of the forest, the first crocus buds popping out of the ground, etc. For me, (a self-proclaimed science nerd) there is nothing more beautiful about nature than a complex biological mechanism that imparts health.

Case in point: breast milk.

Pumped Breast Milk
Image courtesy of Parenting Patch / Wikimedia Commons

We know that breastfeeding is healthy. Beyond the nutrient composition that makes breast milk good food for babies, what else is in breast milk that makes it the liquid gold some moms claim it to be? In particular, what about the claims that breast milk protects against allergies?

An excellent 2010 review in Mucosal Immunology by Verhasselt takes an in-depth look at the mechanisms by which components in breast milk interact with an infant’s immune system. It seems that the route by which breast milk influences allergies all begins in the gut.

Verhasselt begins with the concept of oral tolerance:

Janeway’s Immunobiology defines oral tolerance as, “ The suppression of specific systemic immune responses to an antigen by the prior administration of the same antigen by the oral (enteric) route.”

In plain English this means that by eating and drinking different foods you get used to the antigens (usually proteins that may elicit an antibody response) they contain. As you come to “tolerate” them, your immune system will not produce an inflammatory/allergic response in future encounters with the same antigen.

Achieving oral tolerance to a wide range of antigens is important, so that individuals do not suffer from food allergies.

Breast milk helps achieve oral tolerance in several ways:

First, breastfeeding allows for regular exposure to very small amounts of antigens. Any potential antigens ingested by the mother will be found in her breast milk. This may include common allergens like proteins from cow’s milk, eggs, peanuts, wheat, and even airborne allergens that the mother may be exposed to. These small amounts seems to be an appropriate dose for helping to confer oral tolerance.

Next, the form of the antigens present in breast milk are more easily tolerated by the infant. The processing that a dietary antigen goes through in the mother’s digestive system before it ever reaches her circulation or enters breast milk seems to help confer toleragenic (more easily tolerable) properties when ingested by the infant in this form.

Further, breast milk usually contains high levels of secretory IgA (s-IgA), a class of antibodies that is present in mucosal secretions and is the predominant class of antibodies found in the gut. S-IgA is able to trap food antigens, and while the mechanism is not fully worked out yet, seems to be important in conferring antigen-specific oral tolerance.

In newborns, there is a certain amount of gut permeability—meaning that there are gaps between the epithelial cells that line the intestines. As the gut matures, these gaps close. Increased permeability seems to be associated with the development of allergies. Colostrum (early breast milk) and more mature breast milk contain gut epithelial growth factors which promote gut closure, protecting against any antigens sneaking past the gut barrier.

In addition, breast milk contains a compound called transforming growth factor- β (TGF- β). This is a cytokine (cell-signaling molecule) involved in regulatory T-cell induction which further promotes oral tolerance.

Finally, the bugs. Much recent research suggests that the microbial composition of the gut impacts the immune system. At birth, the gut of the newborn is sterile, but then quickly becomes colonized by microbes. Some microbes are beneficial and other pathogenic. Of the beneficial bugs, some are more helpful than others. For example, Bifidobacterium and Lactobacillus strains of bacteria have been shown to be most beneficial in allergy prevention. Breast milk contains various nutrients (like glycoproteins and oligosaccharides) that promote the growth of these beneficial strains of bacteria.

So, there are several components in breast milk and mechanisms by which this “liquid gold” does seem to contribute to a lower incidence of allergies. These elaborate mechanisms do make me marvel at the beauty of this nature-provided prevention strategy.


Does this mean I should blame my allergies on my mother’s decision not to breastfeed?

Of course not! There are many other factors that figure into the allergy equation—notably genetics, and other environmental exposures.

Does this provide possible avenues for future allergy prevention?

Possibly. It seems to me that if a breastfeeding mother makes a point to eat a variety of foods during lactation—including possible allergens, it may help to promote oral tolerance in her child. Certainly, further research into this strategy as an effective approach is needed.

However, this is pretty interesting research in that seems to challenge the classic advice to parents to avoid giving their children any common allergens in the first year of life.


Murphy, K. (2012). Janeway’s Immunobiology (8th ed.) New York, NY: Garland Science, Taylor & Francis Group, LLC.

Verhasselt, V. (2010). Oral tolerance in neonates: from basics to potential prevention of allergic disease. Mucosal Immunology; 3(4):326-33. doi: 10.1038/mi.2010.25.



mark freedman March 6, 2013 at 4:31 pm

Very interesting, I’m forwarding to many future Mothers.

Lola March 12, 2013 at 10:14 am

Thanks for reading!

Angela March 12, 2013 at 8:31 am

Hi Lola! Thanks for the post. I think the middle part of your post may still be too technical for most people, e.g. ‘breast milk usually contains high levels of secretory IgA (s-IgA), a class of antibodies that is present in mucosal secretions’ or ‘breast milk contains a compound called transforming growth factor- β (TGF- β). This is a cytokine (cell-signaling molecule) involved in regulatory T-cell induction which further promotes oral tolerance’. Especially in this context, it is important to make the information more accessible, especially for mothers who are most vulnerable to persuasion by e.g. companies producing/advertising breast milk substitutes.

Lola March 12, 2013 at 10:19 am

Hi Angela,
Thanks for reading. I really appreciate your input! I am always trying to find the right balance between thoroughly explaining the science and making the information accessible. It is hard to know what is just the right level for my audience. I will try to tone down the technical jargon in the future. Thanks again for the valuable feedback!

Heather d May 7, 2013 at 8:46 am

I actually appreciate having some ‘technical jargon’ as long as it is in moderate doses and further explained in layman’s terms. Have that ‘jargon’ helps to clarify that this is NOT just somebody’s opinion, or some wild misinterpretation of the facts; but that it is in fact based on solid science.

Michelle May 28, 2013 at 11:50 pm

I also appreciate the “jargon” – which is really just accurate detail – as Heather d mentions, as long as it is supported by a plain language summary, it adds to the post. As a scientist who no longer has access behind journal paywalls, I am often frustrated that explanations are too ‘dumbed down’ and often have questions about the mechanisms that aren’t answered. This is especially frustrating when I don’t know whether I can trust the blogger’s knowledge of the science to provide an accurate interpretation of the facts – or if I want to use the information in the article to apply to a related phenomenon.
It must be difficult to find that balance – but perhaps warn those who aren’t interested in the mechanism to follow the plain language summary – or the jargon could go behind a cut for those who want more detail.
Anyway… THANKS for a great article!

Lola Rosewig May 29, 2013 at 7:45 am

Thank you for your comments! I do appreciate the feedback.

Ashley March 24, 2013 at 9:19 am

I’m curious as to how this relates to food sensitivities in breastfed babies. My 8week old started having flecks of blood in her stool, her doctor said it was probably a milk protein allergy, and since I’ve stopped all dairy, the blood had stopped. But this article suggests that ingesting the allergen should help? Just curious as to what causes food sensitivities in breastfed babies if ingesting those foods is
supposed to help prevent them. Thank you! :)

Lola Rosewig March 24, 2013 at 2:16 pm

Hi Ashley,
While breastfeeding is a protective factor against developing food allergies, it is not the only variable in the equation. Genetics also play a big role here. Other factors include infections or disease which may alter the gut microbiota, and what types of antigens to which the infant is exposed and in what dose. Helen’s comment below goes into even more detail. I hope that answers your question. As always, I encourage you to heed your doctor’s advice. And just because your infant may be sensitive to milk protein now, does not necessarily mean that he/she will be when older–as the gut will mature and may be better able to handle these antigens in the future.
Good luck!

Helen March 24, 2013 at 10:23 am

This article suggests that eating a little of everything is good for the breastfed baby’s immune/allergic response. A mother eating a wide variety of foods in as natural a state as possible is usually good both for her AND her breastfed baby. But this is not the case for every mother and baby pair. The problem comes when poor gut health and family allergic history combine to cause a sensitive baby. Food sensitivities in breastfed babies are linked to gut health in the mother. When undigested food proteins drift through your own (leaky) gut wall, they go into your bloodstream and from there into your milk. Some babies are bombarded with these proteins which their mothers are digesting poorly. When there is a history of family allergy either food or environmental, a baby’s risk of allergic symptoms of any kind, to anything, increases. Breastfed babies have a very sensitive early warning system, and will react with vigor to an allergen that they can’t handle, which is also related to THEIR gut health.
Ashley, you have a very smart doctor, and thank heavens you can make your very own “non-dairy” breastmilk. A good naturopath should be able to help you with gut issues of your own, and your baby, and some naturopaths have seen their baby clients lose their allergic response to foods with appropriate probiotic use.

Helen March 24, 2013 at 10:29 am

One more thing–it is very common for a breastfed baby to be supplemented with formula in the hospital, or during the first weeks of life. Just one formula feeding can set a baby up for symptoms of dairy sensitivity weeks later. A formula feeding also alters the baby’s gut flora.

Lola Rosewig March 24, 2013 at 2:18 pm

Helen, thank you for you comments! I agree that there are SO many factors that contribute to allergy risk in infants. I appreciate your contributions to the conversation.

Ashley March 27, 2013 at 12:43 pm

Thank you for helping me! That was very informative and gives me a lot to think about. I exclusively breastfed, but when we were still in the hospital I had to supplement formula for a couple feedings because she could not latch on and got dehydrated. It was scary, but I am so glad that she is doing really well now. Anyway, perhaps that played a part. I also noticed that when I tried reintroducing dairy after the waiting period, to see if it was the culprit, she started having blood in her stool again really quickly, within hours. So perhaps it is also my body that doesn’t absorb things properly.

Nicole April 14, 2013 at 11:08 pm

Hi! I would love some literature on this! I frequently experience supplemental feeding indicated by pediatricians and I think it would be beneficial to my patients if I could prove this to their sometimes misinformed pediatricians! Thank you!

Lola Rosewig April 16, 2013 at 7:53 am

Hi Nicole,
For more information on this topic, the review article I cite by Verhasselt is pretty thorough:
Verhasselt, V. (2010). Oral tolerance in neonates: from basics to potential prevention of allergic disease. Mucosal Immunology; 3(4):326-33. doi: 10.1038/mi.2010.25.
I certainly hope that pediatricians are not misinformed, but can concede that this may happen. But, it is important to remember that pediatricians are likely weighing more variables than just allergy risk when making their recommendations–there may be specific concerns about adequate nutrition, or other maternal or child health issues that are part of the picture. In any event, I hope my post and the reference article help so that you are better informed about the topic.
Thanks for reading!

Heather d May 7, 2013 at 8:51 am

Another potential source for allergic problems in breastfed babies is cesarean sections. Babies born through the birth canal in a normal birth, ingest the maternal flora on the way out, including some from the intestines! It sounds kind of gross, but this is how they get their initial colonization of gut bacteria for their own intestines.

Babies born via surgery skip that important step. They do eventually get colonized from the environment and (ideally) from breastmilk, but studies have shown that they frequently have a *different* composition of gut flora than vaginally-born babies. This could potentially lead to an increased risk of allergies and other gut issues if they are lacking in the most beneficial bugs.

Carlie March 24, 2013 at 11:34 am

Lola, I love your post. I do understand the technicalities of it which makes me very excited to read it. However, most people do need it to be simplified like Angela said above. Thank you for the information. I am going to forward this to my coworkers so we can help educate others about this!

Lola Rosewig March 24, 2013 at 2:18 pm

Thanks for reading and commenting! :)

Sandy March 25, 2013 at 8:02 am

Thank you so much for this post. This topic is near and dear to me. My children are two data points. One, born with an infection, supplemented in the hospital and requiring IV antibiotics reacted to cow’s milk in my diet and later was anaphylactic to milk and peanut. A triple whammy set up in light of the science you made so clear between article and posts. My second was exclusively breastfed, and I maintained an elimination diet based on recommendations of the time. I forget how old she was (over a year at least) before I ate dairy, then waited before direct introduction. I don’t think she knowingly had peanut until about 7. While the elimination diet would no longer be recommended for prevention, the gut health factor could have worked in her favor. While a study of 2 has no real statistical value, the science supports the value of breastfeeding on the individual. Think of all the disruption to gut health caused by antibiotics in mom and baby at birth. And of course frequent supplementation. While life saving at times, perhaps more efforts to avoid those situations and increase breastfeeding could change the food allergy statistics that we can’t quite explain.

Lola Rosewig March 25, 2013 at 9:09 am

Hi Sandy, thanks for sharing your personal experience with this topic!

Shirley Anne peacock March 26, 2013 at 9:36 am

If only my breastmilk had stopped my wee man from getting allergies!! He is 9 months old and has wheat, dairy, rice, corn, banana, tomato and some other fruit allergies and I have eb from birth :( I myself have no allergies but have cut out all to help him!

Lola Rosewig March 26, 2013 at 10:10 am

Hi Shirley,
I’m sorry to hear about your son’s allergies. Like it was brought up in earlier comments, there are so many components to the allergy equation. Other environmental factors or infection could have predisposed him. Who knows? But, good for you that you continued to breastfeed! After all, breast milk still provides excellent nutrition. Good luck with everything!

Leila April 16, 2013 at 2:08 am

I’m sorry to say this but for 4 horrible months I breastfed my allergy ridden son and in the end I wish we would have switched to formula sooner. It was a difficult and courageous act to switch to hypoallergenic formula. My son was a new happier, healthier child and our relationship was so much better. We could leave the house, before then if he was awake he was screaming- for 4 months! For some children breast is NOT best!!!

Lola Rosewig April 16, 2013 at 7:41 am

I absolutely agree that every family needs to do what is best for them. I’m glad to hear that things are better with your son! My only agenda in writing this post was to focus on an interesting biological mechanism, certainly not to tell people what they should or must do. As mothers, we all have to figure out what works best for us.

Worried father June 14, 2013 at 5:45 pm

If breastfeeding could help prevent some allergies, have there been any studies or have you ever heard of parents re-introducing breast milk to kids once they have been diagnosed with allergies? My son is basically allergic to all foods and we would be willing to try anything to help him. Your article really makes us wonder if he could benefit from drinking breast milk at this stage of development. It may sound like a silly thought or suggestion but if it would not hurt him we would be willing to try it.

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