I am having lichen planus on the skin on the lower part of my legs near ankle nd calf...what is the treatment nd why does it happen?

Cortisone cream: Corticosteroids are usually prescribed for lp. There are some other treatments depending on the severity, but that would be at your doctors discretion. Lp is an immune system response and is usually self limiting, meaning it should resolve in 8 to 12 months.

Supportive therapy.: Oral and topical medications are employed to reduce itching and to help resolve the lesion. Antihistamines, topical anesthetics, steroid creams and dressings can help this goal. The cause of lichen planus is not firmly known. Perhaps it is an autoimmune response, a medication reaction or due to exposure to a certain chemical. It is sometimes associated with hepatitis c.