Cause of trembling eyelid

When I learned that I have Mast Cell Activation Disease (MCAD/MCAS), I learned that it is a potential cause of a a trembling eyelid, which is technically known as a blepharospasm. The area under my right eyelid started trembling at least fifteen years ago, but no doctor ever knew the cause of it, and they would usually just say, “Get more rest,” which of course had nothing to do with the problem. As I learned from reading this book about mast cell disease — which is where the image comes from — it turns out that there are ~5,000 mast cells per cubic mm of conjunctival tissue, i.e., the inside of the eyelids.

Photo D8