Diagnosing Milk Allergies in Babies

The National Institute for Health and Care Excellence (NICE) in the UK has published guidelines (March 2025) on Cow’s milk allergies in children and how should you assess a child with suspected cow’s milk allergy. 

If a diagnosis of cow’s milk allergy is suspected on the basis of reported or observed clinical features, the child should be assessed to help distinguish between IgE- and non-IgE-mediated allergy, and managed appropriately.

Allergy-focused history is taken, asking about:

• The symptoms, severity, frequency of occurrence, speed of onset, duration, route of exposure, and the timing of the reaction in relation to cow’s milk exposure. A food and symptom diary may be helpful.
  • Symptoms usually develop within a week of cow’s milk introduction, although they may be delayed for several weeks.
  • Reactions may be triggered by food ingestion, inhalation, or skin contact (rare).
• The form in which milk has been ingested (fresh, processed, cooked, or baked), and the quantity.
  • The trigger is usually cow’s milk, however, it may be cow’s milk protein in maternal breast milk in infants who are exclusively breastfed (rare).
  • IgE-mediated reactions usually occur following a small amount of milk, whereas non-IgE-mediated reactions usually occur after ingestion of larger volumes of milk.
• Any uneventful exposures to cow’s milk before or after the reaction.
• The setting of reactions (such as school or home).
• The reproducibility of symptoms on repeated cow’s milk exposure.
• The age when symptoms started, the child’s feeding history (age of complementary feeding [weaning], breast- or formula-fed), weight gain, and nutritional status.
  • Most affected children become symptomatic by 6 months of age; onset is rare after 12 months of age.
  • If the child is currently being breastfed, ask about the mother’s diet.
• Cultural and religious factors that affect the foods they eat.
• Any other atopic conditions such as asthma, eczema, or allergic rhinitis; any history of other food allergies.
• Any family history of food allergy or atopic conditions, particularly in parents and siblings.
• Any symptom response to elimination and reintroduction of cow’s milk, and/or medications tried, such as oral antihistamines.

Examine the child for:

• Nutritional status and growth, including weight, length/height, and calculation of body mass index (BMI).
• Any signs of a clinical reaction.
• Any signs of allergy-related comorbidities (such as atopic eczema, asthma, and/or allergic rhinitis). See the CKS topics on Eczema – atopic, Asthma, and Allergic rhinitis for more information.
• Any signs suggesting an alternative diagnosis.

Next step is skin prick testing and/or serum-specific IgE allergy testing if there is suspected IgE-mediated cow’s milk allergy:

• Tests in babies should only be undertaken by healthcare professionals with the appropriate competencies to select, perform and interpret them.
• Skin prick tests should only be undertaken where there are facilities to deal with an anaphylactic reaction – usually in the presence of a Clinical Allergist.
• Be aware that there are no reliable allergy tests to confirm the diagnosis of non-IgE-mediated allergy.

IMPORTANT

Do not use the following alternative diagnostic tools to diagnose cow’s milk allergy:

• Serum-specific immunoglobulin (Ig)G testing.
• Vega testing (electroacupuncture devices).
• Applied kinesiology (muscle strength testing).
• Hair analysis (assessing mineral content).
• Atopy patch testing.