You’ve likely experienced it at least once in your lifetime—suddenly your eyelid starts involuntarily twitching in spasms for no apparent reason. When this happens, it’s called myokymia. It’s a common phenomenon, but what causes it?

There is no single, definitive cause for myokymia, but it seems to be rooted in such circumstances as lack of sleep, too much caffeine, increased levels of stress, or prolonged eye strain. Most often, intermittent myokymia is harmless and will resolve on its own. But if spasms persist, you can try alternating hot and cold compresses to sooth the overactive nerve that’s responsible for the twitching.

Occasionally, myokymia can be a sign of dry eye, light sensitivity, pink eye, or be the side effect of certain medications.

If you experience myokymia that continues for more than a week, or your eyelids completely close when spasms occur, call your eye doctor for an examination. In rarer cases, myokymia could be the result of a more serious condition, such as inflamed eyelids (blepharitis) or a nerve disorder.