As researchers uncover the complexities behind cow’s milk allergy in breastfed infants, new evidence suggests that strict maternal dairy avoidance may not always be necessary, paving the way for more personalized and evidence-based management.
Study: Cow’s Milk Allergy in Breastfed Infants: What We Need to Know About Mechanisms, Management, and Maternal Role. Image Credit: Pixel-Shot / Shutterstock.com
Cow’s milk allergy (CMA) is one of the most common food allergies to develop during infancy. A recent review published in the journal Nutrients examines the immunological mechanisms underlying this allergy in breastfed infants, the role of gut dysbiosis, and the effectiveness of an elimination diet approach in its treatment.
The role of cow milk allergens and CMA risk in breastfed infants
CMA occurs in 2.2% of babies during the first year of life, whereas 0.5% of exclusively breastfed babies will be diagnosed with CMA. Certain factors that may impact the risk of developing CMA include age, duration of breastfeeding, and geographic location, with most children acquiring tolerance to this allergy by the age of five.
Cow’s milk contains between 30 and 35 grams of protein per liter, 80% of which is casein and 20% whey proteins, including β-lactoglobulin (β-LG). After consuming milk, caseins and whey proteins are quickly broken down by the stomach, whereas β-LG is relatively resistant to digestion until it reaches the duodenum of the small intestine.
Although β-LG is abundant in cow, goat, and sheep milk, it does not naturally occur in human breast milk. However, after consuming dairy, β-LG can be detected in human breast milk at concentrations ranging from 0 to 800 µg/L. These variations are attributed to differences in maternal physiological absorption of food proteins, as well as the time between dairy intake and β-LG measurement, with peak β-LG levels detected between four and six hours after consumption.
Several studies have reported that high β-LG levels in breast milk are due to prolonged dairy consumption. Comparatively, other studies have reported that peak allergen levels after maternal ingestion of cow’s milk occur between four and six hours.
Nevertheless, β-LG levels in breast milk may correlate with β-LG serum levels in infants, thus confirming that β-LG and other food proteins can enter infant circulation after breastfeeding. Existing evidence suggests that the presence of β-LG and other cow's milk allergens in breast milk does not correlate with an increased risk of CMA in infants, which raises questions about the potential utility of dietary restrictions for breastfeeding mothers.
Symptoms may persist in exclusively breastfed infants with CMA, even when the mother is on a diet free of cow’s milk proteins.”
Immunological types of CMA
CMA can be classified as an immunoglobulin E (IgE)-mediated reaction, non-IgE-mediated CMA, or a mixed form involving both IgE and other cell-mediated responses.
IgE CMA
Approximately 60% of patients with CMA have IgE-mediated CMA, characterized by a type I hypersensitivity reaction that occurs immediately or within two hours after consuming milk. IgE-mediated CMA reactions may include skin rashes, angioedema, runny nose, coughing or wheezing, vomiting and stomach pain, diarrhea, and rarely, anaphylaxis. Skin manifestations occur in all cases.
IgE-mediated CMA rarely affects infants who are exclusively breastfed. However, allergic reactions have been reported in infants who have consumed human milk containing cow's milk proteins.
Forms of non-IgE CMA
Non-IgE CMA typically presents with nonspecific symptoms, most of which affect the gastrointestinal tract, including vomiting, diarrhea, and intestinal inflammation.
Food-protein-induced proctocolitis (FPIP), also known as allergic colitis, is triggered by immune-mediated reactions following exposure to one or more allergens. During FPIP, inflammatory changes in the distal colon and rectum can lead to bloody stools, which may or may not be accompanied by mucus or diarrhea. These symptoms typically present during the first few months of life and usually resolve by about one year of age.
Up to 68% of breastfed infants are diagnosed with FPIP, with cow’s milk proteins responsible for most of these cases, followed by soy, egg, and wheat. About 18% of breastfed infants will be diagnosed with FPIP, with this diagnosis based on the efficacy of a maternal elimination diet.
Several cases of food protein-induced enteropathy (FPE) have also been reported in breastfed infants following exposure to cow’s milk or egg protein in breast milk. FPE can lead to chronic diarrhea, which subsequently causes hypoalbuminemia, swelling of the extremities, weight loss, failure to thrive, abdominal bloating, and recurrent vomiting.
Few studies have considered whether infants were breastfed among those diagnosed with eosinophilic esophagitis, eosinophilic gastroenteritis, and eosinophilic colitis due to CMA, thus limiting the ability to conclude the role of breast milk in affected children. Likewise, Heiner syndrome and other non-IgE-mediated reactions to cow’s milk have not been thoroughly studied in breastfed infants.
Conclusions
Accurate diagnosis and personalized treatment plans are vital to prevent overdiagnosis and ensure proper growth while maintaining the practice of breastfeeding.”
Future studies are needed to standardize diagnostic tools, define CMA symptoms, and identify objective measures of improvement with an elimination diet. Additional research is also required to elucidate the role of elimination diets, the mechanisms involved in allergen transfer through breast milk, and the involvement of the gut microbiota in CMA.
Journal reference:
- Caffarelli, C., Giannetti, A. Buono, E.V., et al. (2025). Cow’s Milk Allergy in Breastfed Infants: What We Need to Know About Mechanisms, Management, and Maternal Role. Nutrients. doi:10.3390/nu17111787