The inclusion criteria:

1. At least 18 years of age and signed written informed consent

2. Clinically and histopathologically diagnosed with OLP according to the modified WHO diagnostic criteria 36 and the newly proposed diagnostic process 37

The exclusion criteria

1. A history of smoking or alcohol abuse

2. Pregnancy, lactation

3. Patient with infectious, allergic, cardiovascular, hematological, endocrine, metabolic and immune‐related diseases

4. Exposure to systemic or topical anti‐inflammatory, immunomodulatory drugs at least within 3 months

5. Patient with concomitant other oral lesions

6. Participant with oral lichenoid reactions, including lichenoid contact reactions, lichenoid drug eruptions and lichenoid reactions of graft‐vs‐host disease

7. Presence of epithelial dysplasia in histopathological examination