BACKGROUND: Lichen planus (LP) is a chronic inflammatory disease of unknown aetiology affecting the skin and oral mucosa. Oral lichenoid lesions (OLLs), like oral contact reactions, may resemble oral lichen planus (OLP) both clinically and histopathologically. As OLP and OLL are hyperkeratotic diseases and filaggrin is essential to keratinization, the distribution of filaggrin may be altered in these lesions. OBJECTIVES: To investigate whether patients with OLP/OLL have (i) altered distribution of filaggrin in the oral mucosa; (ii) a higher incidence of mutations in the filaggrin gene (FLG); (iii) active dermatoses, apart from cutaneous LP, than healthy controls; and (iv) patients with OLP/OLL and a defect in the FLG have more widespread oral lesions and report more symptoms than OLP/OLL patients without a concomitant defect in the FLG. METHODS: Forty-nine Caucasian patients (42 women and 7 men, mean age 61.0 ± 10.3 years), with symptomatic OLP, OLL or stomatitis, and 29 matched healthy controls underwent a clinical oral and dermatological examination, oral mucosal biopsy and filaggrin genotyping (testing for R2447X, R501X, 2282del4). Smear tests for Candida spp. were performed in all patients to exclude oral candidiasis. Immunohistochemistry were performed using poly- and monoclonal filaggrin antibodies. RESULTS: The immunoreactivity for filaggrin was significantly more intense in the oral mucosa in the patients with OLP/OLL compared with healthy controls (P = 0.000025). No difference was noted in the incidence of defects in the FLG and active dermatoses between patients and healthy controls. No difference was noted in extension and number of symptoms reported by patients with OLP/OLL with or without a concomitant defect in the FLG. CONCLUSION: OLP/OLL is associated with an altered distribution of filaggrin in the oral mucosa independently of defects in the FLG. Patients with OLP/OLL did not display more active dermatoses other than cutaneous LP when compared to healthy controls.