Cow's milk protein allergy

Definition/diagnostic criteria Cow’s milk protein allergy (CMPA) is an immune-mediated response to proteins found in cow’s milk. The British Society of Gastroenterology distinguishes between IgE-mediated and non-IgE-mediated CMPA: the former presents with immediate symptoms, while the latter involves delayed reactions.

Epidemiology CMPA affects about 2-3% of infants in the UK, making it one of the most common food allergies in this age group. The prevalence is highest in the first year of life and tends to decrease with age.

Diagnosis
Clinical features:

• IgE-mediated CMPA: Symptoms such as urticaria, angioedema, vomiting and, in severe cases, anaphylaxis, occur within minutes to hours of exposure.
• Non-IgE-mediated CMPA. Often presents with more chronic symptoms like atopic eczema, gastroesophageal reflux disease (GORD) and constipation. Mixed reactions can also occur.

Investigations: Diagnosis primarily involves a detailed clinical history and physical examination. Specific tests may include skin-prick testing or serum-specific IgE testing for IgE-mediated CMPA.

In suspected non-IG-E mediated cases, a pragmatic approach is to make a clinical diagnosis via an elimination diet followed by a milk challenge. Endoscopy and biopsy are rarely needed but can show eosinophilic infiltration in the gut in some cases.

Treatment Management involves the elimination of cow’s milk protein from the diet. For breastfed infants, mothers should exclude all dairy products from their own diets. Formula-fed infants should be switched to an extensively hydrolysed formula (eHF) or, in cases of severe reactions or eHF failure, an amino acid-based formula (AAF). Dietary management should be regularly reviewed via a paediatric dietitian, and additional calcium supplementation may be necessary. For IgE-mediated CMPA, epinephrine auto-injectors may be prescribed for emergency use.

Prognosis The majority of children with CMPA will develop tolerance by the age of three to five years. Regular supervised reintroduction of cow’s milk into the diet is recommended to assess tolerance development. The prognosis is generally better for non-IgE-mediated compared with IgE-mediated CMPA, with a higher rate and earlier development of tolerance.