CMPA Baby Symptoms: Signs Your Baby May Have Cow’s Milk Allergy
Cow’s Milk Protein Allergy (CMPA) is one of the most common food allergies in infants, affecting around 2–7% of babies in their first year. This condition occurs when a baby’s immune system mistakenly sees cow’s milk protein as harmful and reacts against it. CMPA can be particularly distressing for both the child and the parent, especially when symptoms are hard to link back to dairy, e.g. eczema, blood in stool, repeat vomiting some hours later…. Fortunately, recognising the signs early can lead to a timely diagnosis and a manageable treatment plan.
What Is CMPA?
CMPA, also referred to as cow’s milk allergy, is an immune reaction to proteins found in cow’s milk. These proteins, such as casein and whey, can cause inflammation and irritation in various parts of the body.
Unlike lactose intolerance, which is a digestive issue involving sugar in milk, CMPA is an allergic response to the protein in cow’s milk. This means even small amounts of milk protein can trigger symptoms.
CMPA may develop in formula-fed babies and, in some cases, even in breastfed babies.
CMPA Symptoms to Watch For
Symptoms of CMPA can vary widely from baby to baby and may affect multiple systems in the body.
One of the most common signs is skin irritation, including CMPA rash, which presents as red, dry, or itchy patches, sometimes appearing as eczema or hives. These rashes may develop around the face, neck, or folds of the skin. In some cases, facial swelling may also occur after feeding. Digestive symptoms are also frequent and can be misleading, often resembling reflux or colic. Babies may vomit after feeding, experience frequent diarrhoea, or show signs of constipation. Parents notice that their baby cries excessively or arches their back in pain during or after feeds—behaviours that often indicate stomach discomfort or acid reflux associated with dairy allergy. Some babies also show respiratory symptoms, such as a new-onset, post-feed, persistent cough, wheezing, nasal congestion, or noisy breathing. Though these are less common than skin or digestive symptoms, they can appear in moderate to severe cases. Another concern is feeding difficulty. Babies with CMPA may refuse to feed, cry during feeding, or fail to gain weight as expected, all of which suggest that feeding is causing discomfort or pain.
Blood or mucus in the stool is a red flag for cow’s milk protein allergy, although this is a non-IgE variant, known as Cow's Milk Protein-Induced Colitis (CMPIE).
Another form of non-IgE CMP sensitivity is Food protein induced Enterocolitis syndrome (FPIES), typically presenting with profuse vomiting 2-4 hours after food intake. A rash is not noted with this variant.
Frequently Asked Questions
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The typical symptoms of cow's milk allergy (CMA) in infants and young children vary depending on whether the allergy is IgE-mediated or non-IgE-mediated.
IgE-mediated CMA usually presents with acute onset symptoms (within 2 hours of exposure), including vomiting, urticaria, angioedema, erythema, lethargy, and respiratory symptoms such as wheezing or stridor. These symptoms are reproducible with subsequent exposures to cow’s milk protein and typically resolve within hours.
Non-IgE-mediated CMA is characterized by delayed onset symptoms (hours to days after exposure), most commonly involving the gastrointestinal tract. These include vomiting, diarrhea, blood in stools (allergic proctocolitis), chronic diarrhea, regurgitation, abdominal pain, failure to thrive, and persistent crying or irritability. Cutaneous symptoms such as eczema and, less commonly, respiratory symptoms may also occur. The clinical presentation can overlap with common infant symptoms, making diagnosis challenging.
Most infants with CMA have symptoms involving more than one organ system, with gastrointestinal (50–60%), cutaneous (50–60%), and respiratory (20–30%) manifestations being most frequent. Symptoms may be immediate (within 1 hour) or delayed (after 1 hour) following ingestion of cow’s milk protein.
It is important to note that many of these symptoms are nonspecific and common in infancy, so diagnosis should be confirmed by elimination and challenge procedures to avoid misdiagnosis.
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Testing for cow's milk allergy involves a combination of clinical assessment and diagnostic procedures. The process begins with a detailed clinical history and physical examination to assess the likelihood of cow's milk allergy and to characterize the type of reaction (IgE-mediated, non-IgE-mediated, or mixed).
For IgE-mediated cow's milk allergy, the following tests are used:
• Skin prick testing (SPT) with commercial cow's milk extracts or, if unavailable, with fresh milk (prick-prick method). A wheal ≥3 mm larger than the negative control is considered positive. SPT is sensitive but not highly specific, and a negative result has a high negative predictive value, especially in infants.[4][5]
• Serum cow's milk-specific IgE measurement (using assays such as ImmunoCAP or similar). Elevated levels support sensitization, but the predictive value depends on the cutoff used and the clinical context. For example, a specific IgE level ≥2.5 kU/L has a high positive predictive value in infants with a convincing history. However, sensitization alone does not confirm clinical allergy.
• Component-resolved diagnostics (e.g., measuring IgE to casein, α-lactalbumin, β-lactoglobulin) can refine risk assessment and may help predict the likelihood of reaction during oral food challenge.
For non-IgE-mediated cow's milk allergy, SPT and specific IgE are often negative. In these cases, atopy patch testing and emerging biomarkers (e.g., faecal calprotectin) have been studied, but their diagnostic utility is limited and not standardized.
The gold standard for diagnosis is the oral food challenge (OFC), typically performed in a supervised setting after a period of elimination. This is especially important when test results are equivocal or when non-IgE-mediated allergy is suspected.
Allergy Societies emphasize that OFC is required to confirm the diagnosis in most cases, as neither SPT nor specific IgE alone is definitive.
In summary, testing for cow's milk allergy is based on clinical history, SPT, serum-specific IgE, and, when necessary, oral food challenge, with the latter being the definitive diagnostic tool.
Please do get in touch with us if you require testing, we offer all the above modalities.
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In the UK, if an infant has a confirmed or suspected cow's milk allergy, the following milk options are generally considered safe and are recommended under medical supervision:
1. Breastfeeding: Breast milk is the ideal source of nutrition for babies. If a breastfed infant is reacting to cow's milk protein, the mother may be advised to eliminate cow's milk and dairy products from her own diet, but we try not to do this if possible as it is more natural for the allergic infatnt to ‘see’ the cows milk protein through moms diet.
2. Hypoallergenic Formulas: For formula-fed babies, a healthcare professional we will prescribe a special "hypoallergenic" formula. These are not available over the counter and are specifically designed for infants with cow's milk allergy. There are two main types of hypoallergenic formulas:
Extensively Hydrolysed Formulas (EHF): These are the first-line treatment for most cases of mild to moderate cow's milk allergy. The cow's milk proteins have been broken down into smaller pieces, making them less likely to trigger an allergic reaction.
Amino Acid Formulas (AAF): These are used for infants who have severe allergic reactions or who do not tolerate an extensively hydrolysed formula. The protein in these formulas is completely broken down into its individual building blocks (amino acids) and is not based on cow's milk.
Soya-based Formulas (for some infants over 6 months):
Soya-based formulas are not suitable as a first-line alternative for infants under six months of age. For infants over six months, a dietitian may advise on whether a soya formula is appropriate, as some babies with a cow's milk allergy can also react to soya protein.
What to Avoid:
Standard Cow's Milk Formula: This is not safe and will cause an allergic reaction.
Other Mammalian Milks: Milks from other animals like goats and sheep are generally not suitable as they contain similar proteins to cow's milk and are likely to cause a reaction.
Lactose-free Milk: This is not a substitute for hypoallergenic formula as it still contains the cow's milk protein that causes the allergy.
Plant-based Milk Alternatives (e.g., oat, almond, coconut, hemp): These are not nutritionally complete for babies and should not be used as a main milk drink for infants, especially under the age of one. They can, however, be used in small amounts in cooking or on cereal for babies over six months, provided they are fortified with calcium and other essential nutrients, and with the guidance of a healthcare professional.
Rice Milk: Due to its naturally occurring arsenic content, rice milk should not be given to children under 4.5 years old. description
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