Lichen planus occurs when your immune system mistakenly attacks cells of the skin or mucous membranes. No one knows the exact cause of this abnormal immune response. The condition isn’t contagious. In some people, certain factors, such as those below, may trigger lichen planus.
- Hepatitis C infection
- Flu vaccine
- Certain pigments, chemicals and metals
- Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin IB, others) and naproxen (Aleve, others)
- Certain medications for heart disease, high blood pressure or arthritis