Hi, Lichen planus is cosidered autoimmune disease. It may occur on any parts of the body including oral mucosa. Sometime oral lichen planus may occur without skin invovement. Exact cause of oral lichen planus is unknown. In most cases the disease appears unexpectedly and is called idiopathic oral lichen planus. In other cases it may be precipitated by the following.. --Drugs i.e., oral lichenoid drug reaction...,gold therapy,antibiotics, non steroidal anti-inflammatory drugs, drugs used for treating hypertension, heart disease and high lipids.....etc --Contact allergens in dental restorative materials (mercury) or toothpastes, particularly spearmint. These may be identified by careful patch testing --Mechanical trauma..as cheek bite --Viral infection, particularly Hepatitis C You cosult dermatologis for firm diagnosis..The diagnosis of oral lichen planus is often made by its clinical appearance. However tissue biopsy may be helpful, when characteristic features of lichen planus may be observed. I usually manage such case in following ways... -- I advise for proper oral hygiene....as brushing teeth and gums, regular visits to dentist, once-weekly mouthwash with diluted chlorhexidine.If standard toothpaste irritates, I advise to try products that do not contain sodium lauryl sulfate -- I strictly advise to stop smoking -- I suggest to apply topical steroids as drops, pastes, gels or sprays. ----- -- I prescribe Triamcinolone in an emollient dental paste -- I give Steroid injections (intralesional triamcinolone) -- Mouth rinse containing the calcineurin inhibitors: ciclosporin or tacrolimus may be advised -- In severe cases systemic corticosteroids may be used. -- Other possible therapeutic agents may be prescribed..Thalidomide,Systemic retinoids (acitretin or isotretinoin),Griseofulvin,Azathioprine,Cyclophosphamide, Dapsone,Metronidazole,Low molecular weight heparin...etc I hope you got my answer.. Thanks. Dr. Ilyas Patel MD