Lichen planus is an itchy skin rash that usually presents as pink, geometric, raised bumps that can occur anywhere on the body but prefer the wrists, ankles, or genitalia. Lichen planus frequently affects the mouth and appears as erosions or white, wispy patches on the inside of the cheek. Nail changes may also occur with lichen planus. Lichen planus is caused by an immune response by the body. Rarely, hepatitis C infection is a cause for the skin rash. Lichen planus is not contagious. It may be treated by a variety of methods. Topical steroids and other prescription medications, light therapy, and occasionally oral medication is needed to help control the skin eruption.