BACKGROUND: Mast cells have a primary role in atopy. Mast cells may play a unique role in a subgroup of patients with irritable bowel syndrome (IBS). This observation suggests a link between atopic disorders and IBS. OBJECTIVE: To determine whether there is an association between atopic disorders and IBS. METHODS: We undertook a prospective study using structured questionnaires. We administered questionnaires to 125 consecutive patients seen in the following clinics from July 1 through October 31, 2001: allergy/immunology (AI) (n = 39), gastroenterology (n = 36), and general medicine (n = 50). The survey included questions detailing gastrointestinal and allergic symptoms. Diagnosis of IBS was based on Rome II criteria. Diagnosis of atopy was based on clinical parameters. RESULTS: The AI clinic reported a significantly (P = .015) higher rate of IBS than the general medicine clinic. The IBS incidence reported in the AI clinic was similar to that reported in the gastroenterology clinic. The likelihood of IBS was significantly higher in patients with seasonal allergic rhinitis (2.67 times; 95% confidence interval [CI], 1.10-6.49; P = .03), patients with allergic eczema (3.85 times; 95% CI, 1.72-8.60; P = .001), and patients with depression (2.56 times; 95% CI, 1.05-6.14; P = .04). Patients reporting atopic symptoms (seasonal allergic rhinitis, allergic eczema, and asthma) were 3.20 times (95% CI, 1.20-8.50) (P = .02) more likely to fulfill the criteria for IBS. CONCLUSIONS: Adults with atopic symptoms report a high incidence of IBS, suggesting a link between atopy and IBS. We proposed a subgroup of patients with IBS (atopic IBS) who have typical IBS symptoms in association with atopic manifestations. Identifying atopic vs nonatopic IBS may help in identifyingthe underlying pathophysiologic mechanisms and therapeutic options.