36 | Nursing in Practice | Spring 2023
ALLERGY
How to diagnose and manage
cow ’ s milk protein allergy
Dr Toni Hazell advises on how to ensure cow ’ s milk protein allergy is addressed appropriately in primary care
Cow ’ s milk allergy ( CMA , also known as cow ’ s milk protein allergy or CMPA ) is defined by NICE as ‘ a reproducible immune-mediated allergic response to one or more proteins in cow ’ s milk ’. 1 To understand the two different types of CMPA ( IgE and non-IgE mediated ) we need to touch briefly on some of the basics of allergy .
When a person with IgE-mediated CMPA ingests milk , an allergy-specific immunoglobulin ( IgE ) binds to receptors on a mast cell . That mast cell degranulates and releases chemicals such as histamine , which cause symptoms of allergy . The same mechanism causes allergies such as hayfever ( when a person comes into contact with pollen ) and other food allergies . IgEmediated allergy is fairly easy to diagnose , because the reaction usually comes quickly after contact with the allergen ( minutes to a maximum of two hours ), and because raised IgE levels can be measured in a blood test . Non-IgE-mediated allergy is more complicated . The immune process is less clear cut , there are no diagnostic tests and the reaction can come hours after contact with the allergen – sometimes up to 72 hours later , making it much harder to link the two .¹ The list of symptoms used by NICE of IgE- and non-IgE-mediated allergy is shown in the table ( right ). 1 While there is some overlap , broadly speaking IgE-mediated allergy presents with symptoms that a lay person would recognise ( rash , wheeze , itch , swelling ) whereas non-IgE-mediated allergy can present with more vague symptoms , such as loose or bloody stools , food refusal , constipation and failure to thrive .
Careful history and investigation Diagnosis of CMPA depends on a healthcare professional listening carefully to the patient ’ s history ; the symptoms may present during a formal appointment but may just be mentioned in passing when discussing feeding , sleep or other issues . The international Milk Allergy in Primary Care ( iMAP ) guideline 2 is widely used and has easyaccess flowcharts that outline the diagnostic process for both types of CMPA . IgE-mediated allergy is diagnosed in the same way as any other condition – take a history , examine the child and then investigate . This will usually involve a specific IgE blood test , done in primary care , but in some areas your pathway may be referral to an allergy clinic for skin-prick tests .
If non-IgE-mediated allergy is suspected , the only way to make a diagnosis is by implementing a milk-free diet . Formula-fed babies ( whether exclusively or in
CMPA allergy symptoms 1
IgE mediated Speed of symptom onset
Typically rapid onset ( within minutes , up to two hours after ingestion )
Skin Pruritus Erythema Acute urticaria – localised or generalised
Acute angio-oedema , most commonly of the lips , face and around the eyes
Atopic eczema – acute flare-up of pre-existing eczema
Gastrointestinal Angio-oedema of the lips , tongue and palate Oral pruritus Nausea Colicky abdominal pain or discomfort Vomiting Diarrhoea
Respiratory ( usually in combination with one or more of the above )
Lower respiratory tract – cough , chest tightness , wheezing or shortness of breath
Upper respiratory tract – nasal itching , sneezing , rhinorrhoea or congestion ( with or without conjunctivitis )
Other
Symptoms and signs of anaphylaxis or other systemic allergic reactions
Non-IgE mediated
Typically delayed ( usually between two and 72 hours after ingestion )
Pruritus Erythema or flushing Atopic eczema
GORD , vomiting Loose and / or frequent stools Blood and / or mucus in stools Abdominal pain or discomfort Infantile colic , irritability Food refusal or aversion
Constipation ( especially soft stools with excessive straining )
Perianal redness Pallor and tiredness
Faltering growth in conjunction with at least one or more gastrointestinal symptoms . If present , usually indicates severe allergy
Lower respiratory tract symptoms – cough , chest tightness , wheezing or shortness of breath
Note : the list of clinical features is not exhaustive , and the absence of these symptoms and signs does not exclude a diagnosis of food allergy . Mixed IgE- and non-IgE-mediated responses may present with GORD , diarrhoea , constipation and / or eczema . IgE – immunoglobulin E .