Allergy is a term used to describe a specific immune reaction to certain foods. It is not the same as intolerance. Many people are intolerant to certain foods, for example if they eat too much wheat or too many baked beans they develop uncomfortable bloating or wind. This may be associated with other symptoms that cause abdominal pain and loose stools, amongst others. This is not the same as allergy which descibes a particular response driven by the immune system that results in recognition of a component of the food by the immune system and subsequent multi-system response. These type of reactions may be mediated by IgE which can generate anaphlaxis (Associated wheeze, swelling and shortness of breath). Some people also have non IgE related allergy which often results in a more delayed response, but once again this is not the same as intolerance which is commonly associated with IBS.

 

There are reliable tests for foods which cause IgE mediated allergy but not for "delayed" non IgE related allergy or intolerance.

 

Here are some useful Webinars from the NHS https://patientwebinars.co.uk/condition/food-allergy-in-adults/.