Breastfeeding and CMPA: Recognising the Signs
Breastfeeding is the biological norm and offers significant protection for infants in their early months. However, it doesn’t make families immune to challenges. One such challenge is CMPA, which, while less common in breastfed babies (affecting approximately 0.5% compared to 2 to 7.5% of formula-fed infants, The Breastfeeding Network, 2023), can still occur. Diagnosing CMPA can be complex, as its symptoms often mimic typical infant behaviours, leading to both overdiagnosis and missed cases. That said, sometimes it’s screamingly obvious (pun intended).
From a personal perspective, as both a clinician and a mother, I’ve experienced this first-hand. My own baby began crying almost constantly from two weeks old. Her nappies, which had transitioned from meconium to the expected chicken korma yellow, began turning green. She was feeding more than 15 times a day, and by six weeks was producing over eight green, fluid stools daily. I removed all mammalian milk from my diet, and within 72 hours her output dropped to three to four yellow stools a day. However, the crying persisted. It wasn’t until I also eliminated soy from my diet that her symptoms fully resolved. Even trace amounts, like a bite of toast or a biscuit containing soy or dairy, would trigger an immediate reaction: loose green or mucousy stools and renewed crying.
This experience highlights the importance of considering soy as a potential co-allergen. Research suggests that up to 60% of infants with non-IgE-mediated CMPA may also react to soy protein, while around 10 to 14% of those with IgE-mediated CMPA are similarly affected (The Breastfeeding Network, 2023; Frontiers in Nutrition, 2023). When symptoms persist despite the removal of cow’s milk protein, it’s vital to evaluate whether soy might also be a trigger.
What CMPA Is – and Isn’t
CMPA is an abnormal immune response to the proteins in cow’s milk, primarily casein and whey. It is different from lactose intolerance, which involves difficulty digesting milk sugar and is extremely rare in infants under 12 months (NHS Inform, 2022).
There are two main types of CMPA:
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IgE-mediated CMPA: Symptoms develop rapidly (within minutes to 2 hours) and may include hives, vomiting, wheezing or anaphylaxis.
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Non-IgE-mediated CMPA: Symptoms appear later (2 to 72 hours) and typically involve gastrointestinal or skin issues such as reflux, diarrhoea or eczema flare-ups (Allergy UK, 2023).
Approaching Diagnosis
Diagnosing CMPA in breastfed babies can be tricky, especially for non-IgE cases, which make up the majority in this group. There is no reliable test for non-IgE-mediated CMPA. Instead, diagnosis is based on:
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A careful history of symptoms
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A maternal elimination diet, excluding cow’s milk for around six weeks
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A rechallenge to confirm whether symptoms return after reintroducing cow’s milk protein
The Somerset NHS CMPA guidelines state that allergy testing is not helpful for non-IgE CMPA. The gold standard remains a monitored elimination and reintroduction approach (Somerset NHS Foundation Trust, 2022). For suspected IgE-mediated CMPA, referral for skin prick testing or serum IgE testing may be appropriate (BSW Together ICB, 2023).
Impact on Feeding, Bonding and Maternal Wellbeing
The implications of CMPA go far beyond the infant’s physical symptoms. For breastfeeding mothers, managing suspected CMPA can be emotionally and logistically overwhelming.
Research has also shown how overdiagnosis of CMPA, often influenced by commercially biased guidelines, may lead to unnecessary dietary restrictions and increased emotional strain (BMJ, 2018).
Providing clear, evidence-based reassurance and tailored support can help protect maternal wellbeing and preserve breastfeeding where possible.
Best Practice for Introducing Solids with CMPA
Weaning a baby with CMPA requires care, but it should not be a source of fear. UK guidance recommends:
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Starting at around six months (corrected age if premature)
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Offering iron-rich first foods such as lentils, beans, tofu, vegetables and fortified cereals
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Introducing one new food every two to three days to monitor for reactions
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Continuing to avoid all forms of cow’s milk protein, including hidden sources
The First Steps Nutrition Trust offers excellent practical weaning resources tailored to allergenic conditions. These include free downloadable guides for both parents and professionals (First Steps Nutrition, 2021).
Want to Learn More?
If you’d like to explore this topic in greater depth, including how to better support families navigating diagnosis, feeding decisions and emotional wellbeing, join us for our Masterclass:
Understanding Cow’s Milk Allergy in Infants: Symptoms, Diagnosis & Supporting Families.
Whether you’re a healthcare professional, birth worker or simply keen to expand your knowledge, this session will help you feel more confident in spotting the signs, understanding the evidence, and offering meaningful support to families. Click Here for more information.
References
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The Breastfeeding Network. (2023). Cow’s Milk Protein Allergy and Breastfeeding – here.
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NHS Inform. (2022). Food Allergy – here.
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Allergy UK. (2023). Cow’s Milk Allergy in Childhood – here.
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Association of Breastfeeding Mothers. (2023). CMPA and Lactose Intolerance – here.
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Somerset NHS Foundation Trust. (2022). CMPA Guidelines for Breastfed Infants – here.
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BSW Together ICB. (2023). CMPA Diagnosis and Management Pathway – here.
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BMJ. (2018). Overdiagnosis of CMPA and Industry Influence – here.
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First Steps Nutrition Trust. (2021). Infant Feeding Resources – here.
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Frontiers in Nutrition. (2023). Dietary Allergen Cross-Reactivity in CMPA and Soy Allergy – here.
