You’re exhausted after a long day at work. You find yourself slumped in your chair, head in your hands, when your hands slowly begin to creep toward your eyes. Next thing you know, you’re giving your eyes a good rub — and for some reason, you start to feel better.

Turns out, while it might feel pretty damn good, it might not be the best thing for you. While giving your eyes a quick occasional rub to relieve a brief itch is likely harmless, if you’re going to town rubbing them, you could be damaging your vision and making yourself look older.

Why does it feel so damn good to rub your eyes in the first place?

Typically, we feel the urge to rub our eyes when they’re itching or irritated—or simply because we’re feeling stressed, says Anupama B. Horne, M.D., chief for comprehensive ophthalmology at the Duke Eye Center.

“Rubbing stimulates tear production, which can help moisturize dry or tired eyes, and remove any irritating particles,” says Horne. “It can also initiate the oculocardiac reflex, in which pressure on the eyeball causes a slowing of the heart rate and leads to a feeling of stress reduction.”

That’s why you tend to feel better soon after a quick rub — slowing down your heart rate calms you down.

That said, rubbing too hard and too often can damage your eyes and the surrounding structures, explains Dr. Horne. If any dust, eyelashes, or foreign particles are on the surface of your eye, rubbing can lead to scratches on your cornea. A scratched cornea can hurt like hell. It feels like there’s something stuck in your eye that won’t come out, and often comes with tearing, redness, and sensitivity to the light as well.

Another issue with rubbing? You can break the blood vessels on the whites of your eyes, making them look bloodshot. In addition, rubbing can make the skin around your eyes darker — and bloodshot eyes with dark circles can make you look haggard and old beyond your years.

Can rubbing your eyes hurt your vision, too?“On a deeper level, in some genetically or otherwise predisposed patients, excessive rubbing of itchy eyes can cause progressive thinning and shape change of the cornea, known as  keratoconus,” says Dr. Horne.

Keratoconus can significantly decrease your vision. If that happens, you may even need surgery to improve it.

So how do you know if you’re rubbing too much? Take note of whether this eye rubbing is a habit for you. Are you rubbing your eyes every day? Every hour? If you wear contacts, beware rubbing with them in: you can move the contacts around and end up scratching your cornea with the contact.

People who have had LASIK surgery are also at a higher risk of infection from rubbing their eyes.

“LASIK procedures create a flap in the outer layers of the cornea, under which laser is administered to correct vision,” says Dr. Horne. “It is possible that if eyes are rubbed to hard following LASIK that this could cause complications with the flap leading corneal injury.”

Bottom line: Mom was right. If your eyes are bothering you, try some lubricating eye drops instead. And if you’re rubbing to relieve stress, try this stress-reducing breathing technique instead to calm down.