Food allergy or intolerance?

Some clinical conditions can masquerade as food allergies or food intolerances, such as IBS, IBD, dumping syndrome, gastric ulcers, gall bladder disease and pancreatic insufficiency. Therefore, it is important to rule these out. This is often done through a mixture of establishing clinical history, which will help indicate which investigations are most appropriate, and thorough medical examination, where nutritional status should be assessed.  Establishing a diagnosis can involve several stages. Firstly, gathering a clear medical history and having a clinical assessment, then clinical diagnostic tests or a food and symptom diary need to be completed. A diagnostic exclusion diary will then likely be recommended after these have taken place. Finally, an open food challenge with or without double blind placebo-controlled food challenge, which is needed to confirm an allergy or intolerance.

Food Allergy testing

If an IgE mediated food allergy is suspected, then a skin prick test and/or blood tests are often used to detect specific IgE antibodies and any likely co-allergens. The skin prick test will look at suspected triggers and uses commercial solutions or fresh foods to prick the skin. It is only able to measure IgE mediated reactions.  The blood tests can detect allergen specific IgE, and the Radioallergosorbent Test (RAST) is often best used. This method cannot identify non-IgE mediated food triggers and non-immediate adverse reactions. It’s important to note that if patch testing is needed or oral food challenges to diagnose an IgE mediated food allergy, they should only take place where there are resuscitation facilities available e.g., a hospital, as some symptoms can occur quickly and could be life-threatening.

Diagnosing a non-IgE mediated allergy involves establishing a detailed clinical history and assessment – this could also involve a symptom diary. A trial elimination of the suspected allergen may be implemented for around two to six weeks, with a reintroduction after the trial. Again, it’s important that this is completed under medical or dietetic supervision, with the knowledge of appropriate timings of elimination and reintroduction of foods. 

Food intolerance testing

When testing for an intolerance, a similar process is followed with a trial elimination of the suspected food intolerance. After two to six weeks, a reintroduction of the food will occur. Food challenges can also take place, where the suspected food is given orally in small amounts and gradually built up to larger amounts if tolerated – all whilst being monitored.

Alternative Testing

It’s important to note that there are many alternative diagnostic tests out there that should be avoided. This can include the pulse test, vega test, leucocytotoxic test, finger-prick blood tests and hair analysis tests as these tests, have no scientific basis and can lead to misdiagnosis. Furthermore, they could lead to inappropriate dietary restrictions, which could lead to malnutrition.