About half of those who get Lichen Planus also develop mouth sores. the cause of lichen planus isn't known. An identical rash sometimes breaks out in people exposed to drugs containing Gold,Bismuth, Arsenic,Quinine,Quinidine, or Quinacrine and to certain chemicals used to develop color photographs.
Treatment
Drugs or chemicals that may be causing Lichen Planus should be avoided. For people who suffer from itching, an antihistamine such as diphenhydramine,hydroxyzine, or chlorpheniramine may be prescribed,although it may cause sleepiness. Corticosteroids may be injected into the bumps, applied to the skin, or given orally, sometimes with other medications, such as Tretinoin For painful mouth sores, a mouthwash containing Lidocaine may be used before meals to form a pain killing coating
Lichen Planus may disapear and then recur after several years. Prolonged treatment may be needed during outbreaks of this disease,