['The value of specific gastrointestinal symptoms in discriminating irritable bowel syndrome (IBS) from organic disease has been documented. In contrast, there have been few attempts to identify symptoms that discriminate irritable bowel syndrome from food allergy, despite similarities in their respective symptom complexes. We aimed to investigate the value of symptoms in discriminating irritable bowel syndrome from organic disease and food allergy.', 'Subjects (n = 288) were recruited from consecutive patients presenting to the Internal Medicine, Gastroenterology and Allergy Units in Chieti. Patients completed the validated Bowel Disease Questionnaire (BDQ) prior to an independent diagnostic evaluation, which included endoscopy when appropriate. Food allergy was diagnosed using a 2-week elimination diet, followed by a placebo-controlled food challenge test, a skin prick test and serum RAST for specific IgE for suspected foods or additives. The results of the BDQ were not considered in formulating a diagnosis. In total, 99 patients were diagnosed with the IBS, 79 patients were diagnosed with organic disease and 22 patients were diagnosed with food allergy. A further 88 patients with extraintestinal allergies were included as a control group.', 'Based on logistic regression analysis, six symptom items discriminated IBS from organic disease, while five symptoms discriminated patients with IBS from control subjects. A diagnosis of IBS compared to organic disease was positively associated with straining on defaecation (P=0.0001), diarrhoea (P=0.001) and abdominal bloating (P=0.01), but was negatively associated with pain in the upper abdomen (P=0.0004), reflux (P=0.0001) and appetite loss (P=0.004). A diagnosis of IBS compared to extraintestinal allergy was positively associated with pain relieved by bowel movement (P=0.0001), pain in the lower abdomen (P=0.0006), pain in both the upper and lower abdomen (P=0.003), frequent pain (P=0.001) and abdominal bloating (P=0.0009). In comparison between IBS and food allergy patients, a diagnosis of IBS was positively associated with pain in the lower abdomen (P=0.001), pain relieved by bowel movements (P=0.001), frequent pain (P=0.02) and abdominal bloating (P=0.03).'] Do symptoms discriminate irritable bowel syndrome from organic gastrointestinal diseases and food allergy?