Lichen planus is an inflammatory disease that usually affects the skin, the mouth, or sometimes both. It may affect the genital skin as well. The cause of lichen planus is not known. There are cases of lichen planus-type rashes occurring as allergic reactions to medications for high blood pressure, heart disease and arthritis. In those cases, identifying and stopping the use of the drug helps clear up the condition within a few weeks. Some people with lichen planus can also have hepatitis C and your dermatologist may want to check you for this. Lichen planus affects men and women equally, and occurs most often in middle-aged adults. Lichen planus of the skin is characterized by reddish-purple, flat-topped bumps that may be very itchy. They can be anywhere on the body, but seem to favor the inside of the wrists and ankles. The disease can also occur on the lower back, neck, legs, genitals, and in rare cases, the scalp and nails. Thick patches may occur, especially on the shins. Blisters are rare. While the typical appearance of lichen planus makes the disease somewhat easy to identify, a skin biopsy may be needed to confirm the diagnosis.

Sometimes, lichen planus of the skin causes few problems and needs no treatment. However, in many cases there is severe itching. Most cases of lichen planus go away within two years. As it heals, lichen planus often leaves a dark brown discoloration on the skin. Like the bumps themselves, these stains may eventually fade with time without treatment. About one out of five people will have a second attack of lichen planus. There is no known cure for lichen planus but treatment is often effective in relieving itching and in improving the appearance of the rash until it goes away.