Oral lichen planus (OLP) is a chronic disease with immune-mediated pathogenesis. Selenium (Se); an antioxidant, plays a role in modulating immunity. The aim of this clinical trial was to evaluate two Se forms (novel topical hydrogel and oral capsules), solely, in treating erosive OLP based on clinical evaluation and salivary oxidative stress markers. Patients were allocated into one of three groups: group I, topical corticosteroids, group II, topical Se, group III, systemic Se. Treatment lasted for 6 weeks; patients were clinically evaluated at baseline, 6 and 12 weeks. Biochemical analysis for salivary Malondialdehyde (MDA) and Total Antioxidant Capacity (TAC) levels at baseline and 6 weeks was performed. There was a significant reduction in signs and symptoms in response to all treatment modalities. However, there was no significant difference among the 3 groups at 6 weeks. At 12- weeks, group II had significantly lower pain scores compared to group I. Salivary MDA levels showed a significant decrease in patients of group I and group III. TAC levels showed no significant difference in response to treatment. Selenium can be proposed as a treatment for OLP. Salivary MDA levels can be a biomarker for OLP disease severity.