Lichen planus is a disease in which there is an itchy rash on the skin or in the mouth. It is likely to be related to an allergic or immune reaction. Many people get lichen planus (PLAN-us). This disease can develop on one or several parts of the body. It can appear on the skin or inside the mouth. Sometimes, it appears in both places. Lichen planus can even change the way a person’s fingernails or toenails look. It also can appear on the genitals or a person’s scalp.

Lichen planus generally affects adults and can involve any portion of the body, but it has a predilection for the wrists, ankles, and oral and genital tissues. Lichen planus can be quite itchy. Lichen planus can be quite itchy.