Background: Orofacial granulomatosis (OFG) is a chronic inflammatory disorder presenting characteristically with lip swelling but also affecting gingivae, buccal mucosa, floor of mouth, and a number of other sites in the oral cavity. Although the cause remains unknown, there is evidence for involvement of a dietary allergen. Patch testing has related responses to cinnamon and benzoate to the symptoms of OFG, with improvement obtained through exclusion diets. However, an objective assessment of the effect of a cinnamon- and benzoate-free diet (CB-free diet) as primary treatment for OFG has not previously been performed. Thus, this study was undertaken to investigate the benefits of a CB-free diet as first-line treatment of patients with OFG. Materials and Methods: Thirty-two patients with a confirmed diagnosis of OFG were identified from a combined oral medicine/gastroenterology clinic. All had received a CB-free diet as primary treatment for a period of 8 weeks. Each patient underwent a standardized assessment of the oral cavity to characterize the number of sites affected and the type of inflammation involved before and after diet. Results: There was a significant improvement in oral inflammation in patients on the diet after 8 weeks. Both global oral and lip inflammatory scores improved (P < 0.001), and there was significant improvement in both lip and oral site and activity involvement. However, improvement in lip activity was less marked than oral activity. Response to a CB-free diet did not appear to be site specific. A history of OFG-associated gut involvement did not predict a response to the diet. Conclusions: The impact of dietary manipulation in patients with OFG can be significant, particularly with regard to oral inflammation. With the disease most prevalent in the younger population, a CB-free diet can be recommended as primary treatment. Subsequent topical or systemic immunomodulatory therapy may then be avoided or used as second line.