Differentiating milk allergy (IgE and non-IgE mediated) from lactose intolerance: understanding the underlying mechanisms and presentations

Article Figures & Data

IgE mediated	Non-IgE mediated
Skin
Pruritus Erythema Acute urticaria (localised or generalised) Acute angioedema (most commonly in the lips and face, and around the eyes)	Pruritus Erythema Atopic eczema

Gastrointestinal system
Angioedema of the lips, tongue, and palate Oral pruritus Nausea Colicky abdominal pain Vomiting Diarrhoea	Gastro-oesophageal reflux disease Loose or frequent stools Blood and/or mucus in the stools Abdominal pain Infantile colic Food refusal or aversion Constipation Perianal redness Pallor and tiredness Faltering growth plus one or more gastrointestinal symptoms above (with or without significant atopic eczema)

Respiratory system (usually in combination with one or more of the above symptoms and signs)
Upper respiratory tract symptoms (nasal itching, sneezing, rhinorrhoea, or congestion, with or without conjunctivitis) Lower respiratory tract symptoms (cough, chest tightness, wheezing, or shortness of breath)

Other
Signs or symptoms of anaphylaxis or other systemic allergic reactions

	Non-IgE-mediated milk allergy	Lactose intolerance
Symptoms	Gastrointestinal, skin, or respiratory	Bowel only, for example, pain, flatulence, diarrhoea
Mechanism	Immune reaction to milk protein	Non-immune. Reduced ability to digest lactose
Tests	Exclusion diet (NO MILK PROTEIN) (symptom improvement) and then reintroduction (symptom recurrence). May take 4–6 weeks for symptoms to improve	Exclusion diet (LOW LACTOSE) (symptom improvement) and then reintroduction (symptom recurrence). Usually improve within 48 hours of exclusion
Dietary advice (including formulas)	A diet free from cow’s milk protein. Exclude all cow’s milk and products. Consider tolerance acquisition and introduction of, for example, extensively baked products after 6 months	Low lactose diet — exclude cow’s milk and foods containing cow’s milk, although some with low lactose may be tolerated by some individuals
Dietary advice (including formulas)		If secondary, should resolve by 6 weeks