Infant Allergic Reactions to Food Proteins in Human Milk
by Anne Eglash MD, IBCLC, FABM
It is well established that food proteins in the lactating parent’s diet can be found in human milk, such as peanut, egg, cow’s milk and wheat. Many breastfeeding mothers report that removing certain foods from their diet will decrease various infant symptoms such as spitting up, fussiness and infrequent stools. We know that a variety of foods can also trigger allergic proctocolitis (blood-streaked stools in breastfed infants) and removal of these foods in the maternal diet resolves the issue.
Today’s clinical question pertains to the more severe IgE-mediated allergic reactions, including airway swelling, hives, diarrhea and drop in blood pressure.
The study for this week is a systematic review and meta-analysis evaluating the relationship between maternal diet, certain food proteins in human milk and the risk of an IgE-mediated allergic reaction.
Thirty-two studies with participants from 14 countries (mainly high income) were included for evaluation. The studies compared the ‘dose’ of food allergens (egg, cow’s milk, peanut, wheat) in human milk with typical doses that can trigger an IgE-mediated allergic reaction in children.
The researchers found that egg, cow’s milk, peanut and wheat protein were identified in breastmilk. Overall, the amount of these proteins in breastmilk tended to be lower than the typical dose needed to trigger an Ig-E mediated allergic reaction in children.
- There may be a difference in the amount of time from ingestion of the food protein to when the milk samples were obtained.
- The amount of food protein eaten by the lactating parent likely varies between studies.
- The source of the food protein might vary, such as raw eggs, cooked eggs, hen’s eggs, duck eggs.
- There may be individual differences in how well the food protein transfers into human milk.
- There may be differences in how the milk samples are collected, such as pumping a full breast vs taking a 5 ml sample.
See the Answer
Previous reports suggested that food proteins present in human milk (HM) may trigger symptoms in allergic children during breastfeeding, but existing evidence has never been reviewed systematically.
To assess the probability of food proteins in HM to trigger allergic reactions in infants with IgE-mediated food allergy.
Electronic bibliographic databases (MEDLINE, EMBASE) were systematically searched from inception to November 3, 2021. The data regarding the levels of food proteins detected in HM were extracted and compared with data from the Voluntary Incidental Trace Allergen Labelling (VITAL 3.0) guide to assess the probability of food-allergic individuals to experience immediate type allergic reactions on ingesting HM.
A total of 32 studies were identified. Fourteen studies assessed excretion of cow's milk proteins into HM, 9 egg, 4 peanut, and 2 wheat; 3 measured levels of cow's milk and egg proteins simultaneously. We found that levels of all food proteins across the studies were much lower than the eliciting dose for 1% of allergic individuals (ED01) in most of the samples. The probability of an IgE-mediated allergic reaction in a food-allergic infant breastfed by a woman consuming the relevant food can be estimated as ≤1:1000 for cow's milk, egg, peanut, and wheat.
To our knowledge, this is the first systematic review that assesses and summarizes evidence on food proteins in HM and potential for IgE-mediated allergic reactions. Our data suggest that the probability of these being IgE-mediated allergic reactions to food proteins in HM is low.
This systematic review was the first to evaluate studies on the transmission of food proteins into breastmilk and compare the levels to the amount needed to trigger an allergic reaction in children (not infants). The authors recommended that there be a standard with how these studies are done, so that studies can be compared fairly to each other.
Even though the authors report that the amount of food protein in breastmilk tends to be less than the dose typically needed to elicit IgE-mediated reactions in children, we don’t know if recurrent exposure to those low level proteins can increase the risk of IgE mediated reactions over time.
There may also be differences in how food proteins are measured in human milk. Detection methods that look for the whole food protein may miss the partially digested food protein, and those food proteins might also increase the risk of allergic reaction.
The good news, however, is that it is very rare to see a severe IgE-mediated allergic reaction in an exclusive breastfed infant. My recent pubmed search revealed no cases of such reactions among infants who have received donor milk. It makes evolutionary sense that the human body would shield breastfed infants from high exposure to food proteins, in order to prevent the risk of severe allergy.