Welcome @elizabeth6. I moved your question about the causes of lichen planus to this existing discussion so you can connect with others managing lichen planus:
- Lichen planus: https://connect.mayoclinic.org/discussion/lichen-planus-2da636/?commentsorder=newest#chv4-comment-stream-header

According to Mayo Clinic (https://www.mayoclinic.org/diseases-conditions/lichen-planus/symptoms-causes/syc-20351378), 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

Where have the signs of lichen planus appeared for you? How long have you had this?