OBJECTIVE: Irritable bowel syndrome (IBS) is a common gastrointestinal disorder with clinical signs typical of "intestinal" food allergies or intolerance. The aim of this study was to characterize the clinical features of IBS patients suspected of suffering from adverse reactions to food. METHODS: The study involved 128 consecutive IBS patients divided into four groups according to their main symptom on presentation at our outpatient clinic. A detailed medical history was recorded, paying particular attention to any allergies and reported intolerance to food. Each patient was screened for allergies; intestinal permeability tests was performed in randomly selected patients from different groups. Findings were analyzed using the chi2 test. RESULTS: Adverse reactions to one or more foods were reported by 80 patients (62.5%); skin prick tests (SPT) were positive in 67 patients (52.3%) with no significant differences between patients complaining of different symptoms. Patients who reported a food intolerance had more positive SPTs than those who did not (47 of 80 [58.7%] vs 20 of 48 [41.7%]); this difference was not statistically significant, although it suggests a trend (p < 0.0610). There was little consistency between the specific foods reported to cause intolerance and those resulting from the tests (11 of 80 patients, 13.7%). The intestinal permeability test was normal in 29 of 33 patients (87.9%). CONCLUSIONS: More than 50% of IBS patients were found sensitized to some food or inhalant without any typical clinical signs. Patients were unable to identify potentially offending foods. The lack of a correlation between SPT results and reported food allergies needs further investigation to clarify the pathophysiology and improve the diagnosis of intestinal food allergies.