If you’ve ever experienced an involuntary eye twitch, you know it can be quite annoying—but is it a sign of an underlying health problem? Probably not, says Dr. Mira Acs, an optometrist based in Toronto. “I frequently have patients tell me that their eye has been twitching,” she says.  “Most of the time these painless, harmless, unpredictable twitches are an annoyance and nothing else.”

Technically, it’s your eyelid that’s doing the twitching and the proper term for this little quirk is blepharospasm. It’s caused by the part of your brain called the basal ganglion. Though the reason behind these twitches is unknown, doctors do know that it can be aggravated by fatigue, stress, irritation of the inner eyelid, smoking and overconsumption of alcohol and caffeine.

Though blepharospasms are usually harmless, they very rarely act as warning signs of a chronic movement disorder like Tourette Syndrome or Bell’s Palsy. “You should see your optometrist if the twitching is constant for more than two or three weeks, your lid closes completely with the twitch, your face twitches in addition to your eyelids or you have red, swollen or discharging eyes,” Acs advises.