Cow’s milk allergy: Causes, symptoms, and management
Cow’s milk allergy (CMA) is one of the most common food allergies, especially in infants and young children. Formula fed infants are effected the most, while the incidence of CMA in breastfed infants (in response to cow’s milk protein fragments secreted in maternal milk) is very low.
It occurs when the immune system mistakenly identifies proteins in cow’s milk as harmful and triggers an allergic reaction. The main proteins responsible are casein and whey, which can cause reactions even in very small amounts. CMA is different from lactose intolerance. While lactose intolerance involves difficulty digesting milk sugar (lactose) and mainly causes digestive discomfort, cow’s milk allergy involves the immune system and can lead to more severe symptoms.
Symptoms of cow’s milk allergy can appear within minutes or hours/days after consuming milk or milk-containing products. It usually presents with skin (i.e. hives, itching or eczema), gastrointestinal (i.e. vomiting, diarrhoea or abdominal pain) and respiratory symptoms (i.e. coughing or wheezing; severe allergic reaction/anaphylaxis, a life threating reaction) when mediated by Immunoglobulin E (IgE, immediate reactions). The absence of IgE involvement (non IgE mediated, delayed reactions) limits symptoms mainly to the gastrointestinal tract and to a lesser degree to the skin.
Diagnosis is usually made through a combination of medical history, physical examination and allergy tests (i.e. skin prick tests or blood tests) for the IgE mediated CMA, or elimination of cow’s milk followed by planned reintroduction of cow’s milk (milk challenge) for the non IgE mediated one.
The diagnosis of non IgE mediated CMA is challenging as there is no diagnostic test currently available, as opposed to IgE-mediated one where skin and blood testing are widely available. The lack of a diagnostic test often results in over or under diagnosis.
The complexity in diagnosing non IgE mediated CMA is attributed to the fact that the signs and symptoms can overlap with other common childhood conditions such as colic, constipation and gastroesophageal reflux. Although over-diagnosis is more frequently reported both are associated with potentially long-term negative health consequences; multiple dietary alterations/restrictions and often excessive use of anti-reflux medication (i.e. Omeprazole).
The primary treatment for cow’s milk allergy is strict avoidance of cow’s milk and dairy products in both types of allergy. Based on the type of CMA and the severity of the symptoms a hypoallergenic formula milk is offered (such as an extensively hydrolysed or an amino acid–based formula milk) instead of the regular cow’s milk formula. These are only used for the formula fed infants and only for the first 12 months of age. Early involvement of the allergy dietician is strongly recommended to ensure proper nutrition.
Yearly reviews in allergy clinic are required for the management of the IgE mediated CMA; to reassess child’s tolerance to cow’s milk (repeat the allergy tests if needed) and ensure appropriate allergen avoidance measures and an allergy management plan are in place.
The management of a confirmed non-IgE-mediated CMA includes total milk exclusion from the infant’s diet (up to 9-12months of life or for at least 6 months after diagnosis) and milk replacement; maternal milk free diet for breast fed infants and a hypoallergenic formula milk for the formula fed infants or combination of both when needed (mixed feeding).
The clinical management of non-IgE mediated CMA is inherently complex, primarily due to the overlap between allergic symptoms and common functional infant behaviours or gastro-oesophageal reflux disease (GORD). In order to avoid diagnosing with CMA every infant that is frequently unsettled and regurgitates, health professionals are required to follow a diagnostic pathway in order to rule out other causes before diagnosing CMA.
Many infants outgrow cow’s milk allergy by early childhood, although some may continue to have it into adolescence or adulthood. Regular follow-ups in allergy and dietetic clinic is recommended to monitor progress and reassess tolerance. With proper management, infants and children with cow’s milk allergy can lead healthy, active lives while avoiding food allergic reactions.