Cow’s milk intolerance is a type of non-IgE-mediated allergy. It may present as:
- Diarrhoea – may be bloody and/or mucousy
- Faltering growth (less common)
The more symptoms that are involved, the more likely they are to be due to allergy. The only test is exclusion of cow’s milk protein for four to six weeks followed by a rechallenge. This is worth doing for children with eczema not responding to treatment (NICE guidelines) or with multiple symptoms (e.g. eczema associated with diarrhoea). Soya milk can cause symptoms due to cross-reactivity, which can be confusing.
IgE-mediated allergy to milk protein also exists, with much faster onset of symptoms, typically coming on within seconds to minutes of exposure (although can be up to two hours later). Symptoms include:
- Breathing difficulties
- Runny nose/eyes
- BP drop
Allergic urticaria (to any allergen) that has been treated successfully with an antihistamine does not then tend to recur until rechallenge, so if a case of urticaria lasts for days and/or keeps coming back after improving with antihistamines then it’s more likely to be viral urticaria.
Children who have both food allergies and asthma are at risk of anaphylaxis even if they don’t have a history of a severe food allergy reaction, and should carry Epipens.
IgE testing (which has replaced RAST testing) is worth doing even in cases where the history of food reaction is clear-cut, as it can quantify the level of IgE, which gives an idea of the chance of tolerance developing (higher chance in children with initially lower levels) and gives an initial baseline which allows subsequent tests to look for a gradual decline, which would indicate the child has outgrown the allergy. The other thing IgE testing can be useful for, in a child with one identified allergy, is to identify or exclude allergies to foods not yet tried. IgE testing, obviously, isn’t going to be much good in the ‘intolerance’-type symptoms of non-IgE food allergy.
Parents may falsely diagnose food allergy. In one study (reference not given) the prevalence of actual food allergy in children was 5%, but the prevalence of parental belief that their child had a food allergy was 30%. However, the true prevalence has definitely risen over time.
(Pulse learning module)