Lichen planus (LIE-kun PLAY-nus) is an inflammatory condition that can affect your skin and mucous membranes.
On the skin, lichen planus usually appears as purplish, often itchy, flat-topped bumps. In your mouth, vagina and other areas covered by a mucous membrane, lichen planus forms lacy white patches, sometimes with painful sores.
Lichen planus occurs when your immune system mistakenly attacks cells of the skin or mucous membranes. The reason for this abnormal immune response is unknown. You can't catch lichen planus or give it to another person. Most people can manage typical, mild cases of lichen planus at home, without prescribed medical treatment. If the condition causes pain or significant itching, you may need medication to suppress your immune system.