CMPA is the most common allergy in infancy with an estimated prevalence of between 2% and 7.5%, although around 5%-15% of infants display symptoms of an adverse reaction to cow's milk.¹⁰ Both breastfed and bottle-fed infants can develop CMPA with cow's milk protein being obtained from the maternal diet via breast milk or in the formula. CMPA is less common in breastfed infants. Allergy involves a genetic component and so infants with an atopic parent are more likely to develop an allergy, although not necessarily to the same allergen.

The allergic reaction can be IgE-mediated, non-IgE-mediated or a mixture of both.

IgE-mediated reactions can range in severity from mild pruritus and erythema through to angioedema and anaphylaxis. Anaphylaxis is a life-threatening condition that requires emergency medical treatment. Presenting symptoms in infants include difficulty breathing, choking and limpness. IgE-mediated reactions are diagnosed by careful clinical examination and history taking combined with the use of skin prick and blood tests showing the presence of Immunoglobulin-E.

Non-IgE-mediated CMPA is much more complex but is characterised by delayed symptoms, often taking days to develop following exposure to the allergen. Because of this, diagnosis is more complicated and requires the exclusion and reintroduction of foods under strict supervision of a dietitian. Specialist infant formulae, such as Aptamil Pepti, can be used as a diagnostic tool as well as a treatment as their use will lead to rapid disappearance of symptoms. Due to the delayed appearance of symptoms, this type of CMPA can often be confused with a food intolerance, and vice versa.

¹⁰ Definition, diagnoses and management of cow's milk protein allergy. Accessed at https://www.aptamilprofessional.co.uk/pharmacy-learning-modules.