Abstract Background Orofacial granulomatosis (OFG) causes chronic, disfiguring, granulomatous inflammation of the lips and oral mucosa. A proportion of cases have co-existing intestinal Crohn’s disease (CD). The pathogenesis is unknown but has recently been linked to dietary sensitivity. Although allergy has been suggested as an aetiological factor in OFG there are few published data to support this link. In this study, we sought clinical evidence of allergy in a series of patients with OFG and compared this to a series of patients with inflammatory bowel disease (IBD) without oral involvement and to population control estimates. Methods Prevalence rates of allergy and oral allergy syndrome (OAS) were determined in 88 patients with OFG using questionnaires, skin prick tests, total and specific serum IgE levels. Allergy was also determined in 117 patients with IBD without evidence of oral involvement (79 with CD and 38 with ulcerative colitis (UC)). Results Prevalence rates of allergy in patients with OFG were significantly greater than general population estimates (82% versus 22% respectively p =