I have an interesting question to pose which is an extension of the posted question/answer "Does freezing alter the allergenicity of milk?" already submitted by another reader.

I have a 3 month old patient who developed blood and mucous-laden stools while exclusively breastfed by a mother consuming dairy products. The stools have normalized since the strict exclusion of cows' milk in all forms from the maternal diet, a skin test was negative to cows' milk, and the presumed diagnosis is cows' milk protein induced proctocolitis

Mom, however, has almost 1000 cc of breast milk frozen from her commendable efforts at pumping - her baby was in the NICU for a premature gestational age (not extreme; 33+ weeks) and the baby was initially fed pumped breast milk via NG tube to help "feed and grow" - during this time Mom was able to freeze a wonderful supply of milk.

Mom now asks me: can she feed the baby milk from that frozen "stash" that certainly contains cows' milk protein from her diet at the time?

My answer has been: "probably not", as I would suppose that freezing does not denature cows' milk proteins as does heat - but wondering if you had any insight into this at all.


Thank you for your inquiry.

Just so that our readers may conveniently know the response to the previous entry on the effect of freezing on milk allergens, I have copied the response given by Dr. Anna Nowak-Wegrzyn to the question below.

Response from Dr. Nowak-Wegrzyn: "High temperature has a profound effect on whey proteins in cow's milk such as beta-lactoglobulin and alpha-lactalbumin that generally lose their allergenicity with high temperature. Freezing usually conserves protein structure and function, however there might some alteration of a minor specific allergenic epitope that is relevant for an uncommon patient. This might explain why this child tolerated frozen breast milk but not fresh breast milk, assuming that the mother eats dairy products in her diet."

I have not been able to find anything new in the literature in regards to this issue since Dr. Nowak-Wegrzyn’s response, and thus there is nothing additional to add.

As you can see from Dr. Nowak-Wegrzyn’s quote noted above, freezing does not in general alter protein structure and function. But she does state that there may be minor specific allergenic epitopes that could be altered. This response is certainly consistent with the tack you took by telling your patient’s mother that it was “probably not” without risk to allow the infant to ingest frozen breast-milk that contained cow’s milk antigens. But the “probably” is the operative word, and the only certain way to answer the question is to do a feeding trial.

Thank you again for your inquiry and we hope this response is helpful to you.

Phil Lieberman, M.D.

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