“Doctor, I have been diagnosed with IBS but could it be a food allergy instead?” Unfortunately, there is no easy answer to this. Symptoms of irritable bowel such as cramping, loose stools and gas are very rarely due to typical food allergy. The tests done for typical food allergy, scratch tests or blood tests for allergic antibodies are usually unhelpful if the only symptoms the patient has are of the digestive tract. Positive skin tests for food allergy are only helpful in a setting in which the patient’s history suggests an immediate hypersensitivity reaction to foods (ex. hives, rash, swelling, difficulty breathing, etc). Testing often can confirm a strong suspicion of a true food allergy but randomly testing for routine food allergies without a clear indication is rarely helpful.
Which food sensitivity tests should be done in patients with irritable bowel syndrome? Testing for gluten sensitivity (Celiac disease) is more valuable than traditional food allergy testing for a few reasons. First, the prevalence of celiac disease is about 1% in the general population. Second, diagnostic tests for celiac disease are positive four times as often in those meeting criteria for irritable bowel syndrome (Ford et al). To learn more about celiac disease and testing, go to the Celiac Foundation site.
In summary, Yes, IBS may be due to a food hypersensitivity to gluten but the screening tests are simple blood tests and that can be ordered by any doctor. Food Intolerances are even more common causes of gastrointestinal distress. Many patients seeking needlessly pay many hundreds of dollars for useless IgG tests for food allergy. These have no value whatsoever.
Ford AC, Chey WD, Talley NJ et al. Yield of diagnostic tests for celiac disease in individuals with symptoms suggestive of irritable bowel syndrome: systematic review and meta-analysis. Arch Intern Med. 2009 Apr 13;169(7):651-8.