Perceived food and drug allergies in functional and organic gastrointestinal disorders

Background: Gastrointestinal symptoms are often due to functional disorders. Many individuals with abdominal symptoms believe they are allergic to or intolerant of various foods. Aim: To assess whether self-reported allergy is linked to a subsequent functional or organic diagnosis. Methods: One thousand new patients attending a district hospital gastroenterology clinic completed a questionnaire about believed drug and food allergies and foodstuffs thought to worsen symptoms. No attempt was made to confirm patients' self-reported allergies or intolerances. Final diagnoses were classified as organic or functional. Results: Nineteen per cent of patients reported drug allergies, 14% reported food allergies and 30% identified foods that worsened symptoms. Atopic patients reported more allergies. Forty-eight per cent of patients had a functional diagnosis. Women were twice as likely as men to have a functional diagnosis. Patients subsequently diagnosed with a functional disorder were more likely than those with organic disease to report drug allergies (odds ratio, 1.92; 95% confidence interval (Cl), 1.39-2.65), food allergies (odds ratio, 4.14; 95% CI, 2.73-6.26) or foods that worsened their abdominal symptoms (odds ratio, 3.08; 95% CI, 2.31-4.10). The likelihood of symptoms being functional increased even further if adverse reactions to both drugs and foods were reported. Patients with weight gain were more likely to report food allergy, and those with both features were very likely to have a functional disorder (odds ratio, 4.58; 95% CI, 3.08-6.86). Conclusions: Patients with gastrointestinal symptoms who report drug or food allergies or worsening of symptoms with various foods are more likely to have functional than organic illness. Enquiry about perceived allergies and intolerances may help in the early identification of functional gastrointestinal disorders.