Cow's-milk protein allergy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Milk contains several allergenic proteins, principally casein and whey proteins. Allergy can involve IgE antibodies, cellular non-IgE mechanisms or a mixed process, producing different timing and organ patterns.

IgE cross-linking on mast cells rapidly releases histamine and other mediators. This explains urticaria, angioedema, bronchospasm and cardiovascular collapse soon after exposure.

Non-IgE inflammation is slower and primarily affects skin and gut. No validated routine blood or skin test diagnoses it, so a controlled elimination-and-reintroduction sequence is essential.

Common infant behaviours overlap: physiological reflux, colic, loose stool and eczema occur without allergy. Multiple vague symptoms should not lead automatically to expensive formula or maternal exclusion.

History records the precise milk form, amount, interval to symptoms, reproducibility and treatment. Baked milk may be tolerated differently from fresh milk, but families should not test this after an immediate reaction without advice.

Breastfeeding can continue because maternal exclusion, when genuinely needed, removes dietary cow's-milk protein fragments while preserving breast-milk benefits. Dietitian input prevents calcium, iodine, protein and energy deficits.

Extensively hydrolysed formula breaks proteins into smaller peptides tolerated by most affected infants. Amino-acid formula contains no intact peptide and is reserved for higher-severity or hydrolysate-unresponsive disease.

Formula selection must consider age, nutritional completeness, palatability and mechanism. Lactose content is not the defining issue; some appropriate hypoallergenic formulas contain lactose.

Diagnosis should have a review point. A failed elimination suggests another cause, while improvement followed by recurrence on reintroduction supports non-IgE allergy.

Most children acquire tolerance, especially in non-IgE disease. Timing and setting of reassessment depend on phenotype, age, asthma, prior severity and test results.

Emergency planning includes avoidance, label reading, childcare communication and adrenaline autoinjector training when prescribed. Devices supplement, not replace, calling emergency services.

Family language should separate risk from blame. Accidental exposure is common, and a practical plan is safer than an unrealistically broad household ban.

Key points

Cow's-milk protein allergy is immune mediated. Lactose intolerance is not milk allergy and is uncommon as a primary disorder in young infants; lactose-free formula still contains cow's-milk protein.
IgE-mediated allergy usually produces reproducible symptoms within minutes to 2 hours: urticaria, angioedema, wheeze, cough, vomiting, hypotension or collapse.
Non-IgE allergy is delayed over hours to days and may cause eczema, diarrhoea, constipation, blood or mucus in stool, vomiting, reflux-like distress or faltering growth; these symptoms are nonspecific.
First-line diagnosis is an allergy-focused history covering timing, dose, reproducibility, systems involved, feeding, growth, eczema and previous treatment. Do not order indiscriminate food panels.
For suspected IgE allergy, skin-prick testing or serum specific IgE supports diagnosis only when interpreted against history. Test magnitude does not predict future reaction severity.
For mild-to-moderate suspected non-IgE allergy, use a 2–6 week cow's-milk protein elimination followed by planned reintroduction. Improvement without relapse on reintroduction does not confirm allergy.
A medically supervised oral food challenge is the reference standard when diagnosis remains uncertain or specialist reassessment of tolerance is needed; it is not undertaken in primary care for suspected immediate allergy.
Continue breastfeeding. If symptoms occur through breast milk, a time-limited maternal dairy elimination may be tried with dietitian support, calcium and vitamin D, followed by reintroduction to confirm causality.
For formula-fed infants, an extensively hydrolysed formula is first line for most mild-to-moderate cases. Use amino-acid formula for severe disease, anaphylaxis, significant faltering or failure of an adequate hydrolysate trial with specialist input.
Goat's- and sheep's-milk formulas cross-react and are unsuitable. Partially hydrolysed and comfort formulas do not treat allergy; soy is generally avoided under 6 months and needs individual assessment thereafter.
A home milk ladder is for selected confirmed non-IgE allergy under clinician or dietitian direction. It is unsafe after anaphylaxis or other significant immediate reactions unless the allergy team explicitly plans it.
Review the diagnosis and test for tolerance. Unnecessary long-term exclusion impairs nutrition, increases cost and may increase anxiety around food.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

IgE-mediated sensitisation

Milk-specific IgE primes mast cells, allowing rapid mediator release after re-exposure to casein or whey proteins.

Non-IgE immune response

Cell-mediated gastrointestinal or cutaneous inflammation creates delayed symptoms without positive immediate-allergy tests. despite genuine immune-mediated disease.

Atopic susceptibility

Eczema and other atopic disease increase the probability of food sensitisation but do not prove milk is causing symptoms.

Misattributed common symptoms

Physiological reflux, colic, infection and feeding mechanics frequently imitate allergy and drive false diagnosis without confirmation.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Immediate mediator release
Mast-cell histamine and lipid mediators increase vascular permeability, smooth-muscle contraction and mucus secretion within minutes. and can destabilise circulation.
2
Delayed mucosal inflammation
Cellular immune activation disrupts gastrointestinal mucosa, motility and absorption over hours to days. and sometimes causes occult blood loss.
3
Skin-barrier interaction
Inflamed eczema increases sensitisation risk, while food-triggered inflammation may worsen dermatitis in a subset rather than all affected infants.
4
Nutritional consequence
Vomiting, enteropathy and restrictive substitution can reduce energy, protein and micronutrient availability and impair growth. during a vulnerable developmental period.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Timing and reproducibility

Record exact food, form, amount, interval, organ systems, duration, treatment and whether the same exposure repeatedly causes symptoms.

Immediate phenotype

Identify hives, swelling, cough, wheeze, voice change, vomiting, pallor, hypotension or collapse within minutes to 2 hours.

Delayed phenotype

Assess eczema, stool, blood or mucus, vomiting, discomfort and constipation over hours to days, while recognising low specificity.

Nutrition and growth

Plot weight and length and review breast milk, formula, exclusions, supplements, calcium, vitamin D and complementary-food diversity.

Risk and preparedness

Review asthma, prior reaction severity, adrenaline access, label reading, childcare plan and caregiver confidence.

Red flags requiring action

Stridor, wheeze, persistent cough, tongue swelling, collapse or altered responsiveness after milk is anaphylaxis until proved otherwise.
Poor perfusion, lethargy or repetitive vomiting 1–4 hours after ingestion may represent food protein-induced enterocolitis and requires urgent assessment.
Bilious or projectile vomiting, abdominal distension, haematemesis or substantial rectal bleeding requires evaluation for surgical, infectious or inflammatory disease.
Faltering growth, hypoalbuminaemia, iron deficiency or extensive enteropathy needs paediatric and dietetic assessment and may require amino-acid formula.
Respiratory symptoms during a feed may indicate aspiration rather than allergy; assess swallowing and cardiorespiratory state.
Multiple food exclusions, severe eczema, parental fear or lack of an affordable replacement risks malnutrition and needs early specialist support.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line: allergy-focused historyFirst stepFirst line
Why
Estimate mechanism and pre-test probability before testing or elimination.
Interpretation and limitations
A reproducible rapid multi-system reaction supports IgE allergy; nonspecific delayed symptoms require controlled elimination and reintroduction.
02
Skin-prick or serum specific IgE
Why
Support suspected immediate milk allergy.
Interpretation and limitations
A positive result shows sensitisation, not necessarily clinical allergy or severity; interpret against history and never use broad food panels.
03
Diagnostic elimination and reintroduction
Why
Confirm mild-to-moderate suspected non-IgE allergy.
Interpretation and limitations
Symptoms should improve during 2–6 weeks of complete protein exclusion and reproducibly recur with planned reintroduction; no relapse argues against diagnosis.
04
Reference standard: supervised oral food challengeReference standard
Why
Resolve diagnostic uncertainty or reassess tolerance in a controlled setting.
Interpretation and limitations
Objective symptoms at a defined cumulative exposure confirm clinical reactivity; setting and protocol reflect prior risk.
05
Targeted nutrition and gastrointestinal tests
Why
Assess significant bleeding, anaemia, hypoalbuminaemia, faltering growth or alternative disease.
Interpretation and limitations
Results guide severity and differentials but no routine blood marker confirms non-IgE cow's-milk allergy.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Physiological reflux or colic

A thriving infant with regurgitation or crying but no reproducible immune pattern commonly has a normal developmental condition.

Lactose intolerance

Carbohydrate malabsorption causes bloating and acidic diarrhoea, often transiently after gastroenteritis, without urticaria or anaphylaxis. or cardiovascular involvement.

Infection or surgical disease

Gastroenteritis, UTI, sepsis, pyloric stenosis and obstruction require attention to fever, dehydration, projectile or bilious vomiting.

Swallowing dysfunction

Cough, wet breathing, cyanosis and recurrent chest infection linked to feeds suggest aspiration rather than allergy.

Other gastrointestinal inflammation

Coeliac disease, eosinophilic oesophagitis and inflammatory bowel disease become relevant with age, dysphagia, anaemia or persistent symptoms.

Additional chapter-specific clues

Alternative disease

Examine hydration, abdomen, skin, respiratory system, mouth, swallowing and development for infection, obstruction, aspiration or systemic illness.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ImmediateTreat and refer IgE allergyFirst stepMilk causes rapid objective skin, respiratory, gastrointestinal or circulatory symptoms.

1Treat anaphylaxis immediately with intramuscular adrenaline and emergency services.
2Avoid milk, obtain allergy testing through an appropriately competent service and provide a written emergency plan.
3Arrange dietitian review and specialist-supervised challenge or tolerance reassessment according to risk.

02DelayedEliminate then reintroduceMild-to-moderate delayed symptoms fit non-IgE allergy after alternatives are assessed.

1Undertake complete cow's-milk protein exclusion for 2–6 weeks with nutritionally complete substitution.
2Record symptom and growth response without adding multiple simultaneous exclusions.
3Reintroduce in a planned age-appropriate way to confirm recurrence unless severity requires specialist supervision.

03BreastfedPreserve breastfeedingA breastfed infant has a convincing delayed phenotype.

1Continue breastfeeding and remove direct cow's-milk protein from the infant diet.
2Consider a time-limited maternal dairy exclusion only with calcium, vitamin D and dietitian support.
3Reintroduce maternal dairy to confirm causality and stop restriction if symptoms do not reproducibly return.

04FormulaChoose by severityA nutritionally complete breast-milk substitute is required.

1First lineUse extensively hydrolysed formula first line for most mild-to-moderate disease.
2Use amino-acid formula with specialist input for severe disease, anaphylaxis, marked growth effect or hydrolysate failure.
3Review acceptance, growth, symptom response and the planned tolerance-assessment date.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

First-line emergency medicine for suspected life-threatening anaphylaxis.

Adrenaline 1 mg/mL intramuscular injection

Suspected anaphylaxis: 0.01 mL/kg intramuscularly into the anterolateral thigh, maximum 0.5 mL; repeat after 5 minutes if airway, breathing or circulation problems persist.

Call 999, do not delay for antihistamine, and use the intramuscular route. Autoinjector doses follow age or weight and the prescribed emergency plan; arrange observation and specialist follow-up.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Anaphylaxis

IgE-mediated exposure can cause rapid respiratory or cardiovascular collapse requiring intramuscular adrenaline. without waiting for skin changes.

Growth and micronutrient deficit

Active enteropathy or poorly replaced dairy exclusion may reduce energy, calcium, vitamin D, iodine and protein.

Feeding aversion

Pain, vomiting and anxiety around exposure can lead to texture refusal and prolonged distressed meals. and restricted dietary variety.

Diagnostic entrenchment

Failure to reintroduce or challenge can preserve a false label, costly formula use and unnecessary restriction.

Accidental exposure

Inadequate label, nursery or emergency planning increases avoidable reactions and family fear. across home and childcare settings.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Plot weight and length and review symptom trajectory after a single defined dietary change.
Check formula volume, acceptance, preparation and supply; prescriptions are ineffective when the infant refuses the taste.
For maternal dairy exclusion, assess calcium, vitamin D, iodine, protein and total energy with a dietitian.
Ensure allergens not implicated remain in the diet to preserve variety and tolerance.
Review adrenaline device dose, expiry and technique at each relevant contact when prescribed.
Document nursery or school plans and train caregivers to recognise anaphylaxis.
Set a date to reassess diagnosis and tolerance rather than renewing exclusion indefinitely.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Lactose is not protein

A lactose-free cow's-milk formula removes carbohydrate but retains allergenic protein and therefore does not treat cow's-milk protein allergy.

Response alone is insufficient

Symptoms such as crying fluctuate naturally; diagnostic reintroduction is what links improvement specifically to milk-protein exclusion.

Test size is not severity

Specific IgE and wheal size can estimate likelihood of reaction but cannot promise that the next reaction will be mild.

Hydrolysate is first line for most

Amino-acid formula is valuable in severe disease but routine first use increases cost and may perpetuate diagnosis without added benefit.

A ladder is phenotype specific

Gradual baked-milk introduction can suit selected non-IgE cases but is not a generic home test after immediate systemic reactions.

11Common pitfallsFrequent interpretation and management errors.

01
Do not diagnose allergy from reflux or crying alone.
02
Do not use food-specific IgG testing, hair analysis or broad screening panels.
03
Do not prescribe lactose-free or goat's-milk formula for cow's-milk protein allergy.
04
Do not conduct a primary-care challenge after an immediate systemic reaction.
05
Do not start multiple exclusions at once and then claim one allergen is confirmed.
06
Do not continue maternal dairy exclusion without supplementation and diagnostic reintroduction.
07
Do not use a home milk ladder for previous anaphylaxis unless the specialist team directs it.
08
Do not renew specialist formula indefinitely without growth and tolerance review.