Lactose intolerance and cow’s milk allergy

I’ve been going through some old journals. The August ’16 BGJP had a useful article on lactose intolerance and cow’s milk protein allergy.

Lactose intolerance

A digestive problem caused by reduced ability to digest lactose (as distinct from cow’s milk protein allergy which is an immune-mediated reaction).

Primary lactose intolerance – caused by natural reduction in lactase levels after about the age of 3.

Secondary lactose intolerance -caused by mucosal or epithelial damage – severe gastroenteritis, coeliac disease, cow’s milk allergy.

(Congenital lactose intolerance – very rare occurrence in some isolated populations.)

Symptoms are bowel-related only – abdominal pain, bloating, flatus, diarrhoea. It does not cause rectal bleeding. It also doesn’t cause any non-bowel symptoms; when these are triggered by milk, it’s likely to be due to cow’s milk protein allergy.

Symptoms will normally clear up within 48 hours on a low lactose diet. (Breastfeeding is supposed to be continued; I’m not sure of the evidence base or how that works out.) Secondary lactose intolerance typically resolves within about six weeks on a lactose-free diet.

Cow’s milk allergy

May be IgE-mediated or non-IgE-mediated (which still involve the immune system). IgE-mediated reactions typically develop immediately and non-IgE-mediated after up to 48 hours delay. Non-IgE-mediated reactions can be confused with lactose intolerance (or with milk protein intolerance; they are actually allergies rather than intolerances).

Abdominal pain, diarrhoea, and pruritus and erythema of the skin can be caused by either. Other than that, they have separate sets of possible symptoms (as well as developing symptoms on different timescales):


  • Urticaria (localised or generalised)
  • Angioedema
  • Oral pruritus
  • Nausea
  • Vomiting
  • Respiratory tract symptoms, both upper and lower (including conjunctivitis, cough, nasal congestion, and symptoms of hay fever/rhinitis)
  • Anaphylaxis


  • Atopic eczema
  • GORD
  • Blood/mucus in the stools
  • Infantile colic
  • Food refusal/aversion
  • Constipation
  • Perianal redness
  • Pallor
  • Tiredness
  • Faltering growth associated with at least one gastrointestinal symptom

Skin prick or blood tests should be done for suspected IgE-mediated milk allergy but isn’t necessary for suspected non-IgE-mediated milk allergy.

Treatment for a breast-fed baby is for the mother to go on a dairy-free diet with calcium supplementation. For a formula-fed baby (or a breast-fed baby whose mother would prefer to wean), the first-line treatment is extensively hydrolysed formula, except in cases of severe symptoms where the first line of treatment should be an amino acid formula. Amino acid formulas should also be used for formula-fed babies who continue to have symptoms on extensively hydrolysed formula, and for breast-fed babies with cow’s milk allergy who require top-up feeds.

Do not use:

  • Goat’s milk – too much cross-reactivity
  • Soya milk – also cross-reactive (up to 14% in IgE-mediated allergy and up to 60% of those with non-IgE-mediated allergy), but also weak oestrogenic effect of isoflavones
  • Rice milk – too high an arsenic content to be used in children <4.5 yrs.

Retrial of cow’s milk protein can be considered after six months on a CMP-free diet. Tolerance to extensively baked milk products is likely to occur before tolerance to less well-cooked products.


About Dr Sarah

I'm a GP with a husband and two young children.
This entry was posted in Allergies, Credits 2017, Food allergy, Food intolerances. Bookmark the permalink.

One Response to Lactose intolerance and cow’s milk allergy

  1. Pingback: Food allergy | A Spoonful Of Sugar

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