Lichen planus  is a condition that can cause swelling and irritation in the skin, hair, nails and mucous membranes. On the skin, lichen planus usually appears as purplish, itchy, flat bumps that develop over several weeks. In the mouth, vagina and other areas covered by a mucous membrane, lichen planus forms lacy white patches, sometimes with painful sores.

Most people can manage typical, mild cases of lichen planus at home, without medical care. If the condition causes pain or significant itching, you may need prescription drugs. Lichen planus isn't contagious.

SYMPTOMS

The signs and symptoms of lichen planus vary depending on the areas affected. Typical signs and symptoms are:

• Purplish, flat bumps, most often on the inner forearm, wrist or ankle, and sometimes the genitals
• Itching
• Blisters that break to form scabs or crusts
• Lacy white patches in the mouth or on the lips or tongue
• Painful sores in the mouth or vagina
• Hair loss
• Change in scalp color
• Nail damage or loss

CAUSES

Lichen planus occurs when your immune system attacks cells of the skin or mucous membranes. It's not clear why this abnormal immune response happens. The condition isn't contagious.

Lichen planus can be triggered by

• Hepatitis C infection
• Flu vaccine
• Certain pigments, chemicals and metals
• Pain relievers, such as ibuprofen (Advil, Motrin IB, others) and naproxen (Aleve, others)
• Certain medications for heart disease, high blood pressure or arthritis