Causes

It's not known what causes oral lichen planus. However, T lymphocytes — certain white blood cells involved in inflammation — appear to be activated in oral lichen planus. This could indicate an immune disorder, and genetic factors may be involved. But more research is needed to determine the exact cause.

It's possible that, in some people, oral lichen planus may be triggered by certain medications, mouth injury, infection or allergy-causing agents such as dental materials. Stress may be involved in symptoms becoming worse or recurring. However, these causes are not confirmed.