Ask the doctor: My daughter has been diagnosed with IBS but maybe she has a food intolerance. Should we have her tested?

The cause of children’s tummy pain is notoriously difficult to diagnose. Photo: Getty Images/iStockphoto

Jennifer Grant

February 06 2023 02:30 AM

Question: My daughter has suffered terribly with her tummy and has been going to her GP for a year with no joy. She has been sent for tests and her GP says there is not much else she can do and that my daughter has IBS. I wonder is there any alternative ways of looking at this. A friend told me of a food intolerance test that involves sampling hair that did wonders for her daughter. It is very expensive so I was wondering if you had any thoughts on it?

Answer: I think you would be wasting your money paying for expensive hair testing to reveal supposed food intolerances. This kind of testing, when subjected to appropriate scientific evaluation, demonstrates a lack of reproducibility and a lack of any association with disease. There is no role for hair analysis, isolated IgG testing, Kinesiology, Vega testing or Enzyme Potentiated Desensitization, Acupuncture or Naturopathy for diagnosing or managing food allergy or intolerance.

Besides, tummy pain in children is notoriously non-specific and it is very reassuring that your GP has ruled out all the major Gastro-Intestinal (GI) disorders such as coeliac disease or inflammatory bowel disease. Allergy tests are of no value in the investigation of abdominal symptoms in children.

I suggest you look at the social, emotional and developmental milestones for your child. Is she having any difficulties learning in school? Have any of her teachers ever expressed any concerns about possible dyslexia, dyscalculia, dyspraxia or noticed her being sad or crying in class? Does she have a good network of kind, supportive friends? Is she engaging happily in after-school activities?

Food intolerance generally causes GI symptoms such as excessive intestinal gas, bloating, abdominal pain, diarrhoea, but other symptoms like skin rash/itch or headache may also occur. The amount of food ingested is directly related to the severity of symptoms, and ingestion of the food causes similar symptoms every time. There is currently no validated test to confirm delayed or non-IgE mediated food allergy or food intolerance (cell mediated/Type IV hypersensitivity).

In general, children with a real food allergy (much more serious than food intolerance) have other atopic conditions, especially eczema, occasionally asthma and allergic rhinitis. The exact incidence is unknown but is likely to be very similar to that in the UK — 3-6pc of preschool children and 1-2pc of older children and adults.

The most common food allergens in infancy and childhood are cows’ milk, egg, peanut and tree nut, fish and shellfish account for more than 90pc of cases. Most children will outgrow allergy to milk or egg. Most children will not outgrow a peanut, tree nut, seed, fish or shellfish allergy. Wheat allergy is extremely rare and presents in early infancy with severe urticarial reactions and therefore is easy to recognise. The current best way to aid a diagnosis of food allergy is with skin prick and blood tests to assess the production of IgE antibodies to the specific allergen.

Specific IgE allergy testing has relatively low positive predictive value (approx. 50pc) and should only be tested for only two or three suspected foods. On the contrary, a negative IgE test results are highly specific and have a negative predictive value of 95pc for milk, egg and peanut. These tests have no relevance in the investigation of abdominal symptoms such as constipation, diarrhoea, bloating or abdominal pain. It is important to consider food allergy in children with refusal to feed, severe aversive feeding behaviour, problems progressing the weaning diet, failing to reach predicted growth milestones plus one or more GI symptoms, especially if they also have eczema that is difficult to control.

The best way to approach your concerns about your child’s food intolerance is under expert guidance with a registered dietician who can supervise the limitation of certain food exclusion and reintroduction. This should be time defined (four to six weeks in duration) and exclude no more than four foods.

Dr Jennifer Grant is a GP with Beacon HealthCheck