The cause of oral lichen planus has not been clearly defined, and it is currently believed that it may be related to immune, mental or infectious factors. 1. Immune factors: studies have shown that disorders of the immune system, low immunity, etc. will increase the chance of lichen planus. 2. Psychological factors: mental stress, depression or anxiety may increase the risk of developing lichen planus or aggravate the symptoms; psychological treatment may relieve some of the symptoms. 3. Infectious factors: viral infections, bacillus, spirochete or fungal infections may lead to lichen planus. There is no specific treatment for lichen planus. It is recommended that the cause of the disease be identified and treated, and that localized symptomatic treatment be given to alleviate the symptoms.