What causes vasculitis?

What causes vasculitis?

In most cases, the exact cause is unknown, but the immune system (which helps keep the body healthy) plays a role. While the immune system usually works to protect the body, it can sometimes become "overactive" and attack the body. In most cases of vasculitis, something causes an immune or "allergic" reaction in the blood vessel walls.

Substances that cause allergic reactions are called antigens. Sometimes certain medicines or illnesses can act as antigens and start this process.