The wrong eyeliner technique won't just make your makeup look bad or outdated. If you line the inside of your lash line, your makeup may wear off faster, mess with your vision, and lead to icky eye disease, according to a new study recently published in the journal Eye and Contact Lens, which was the first of its kind to track eyeliner migration on video.
Researchers used a glittery eyeliner pencil to apply liner either the inside or outside the lash lines of three women on two separate occasions. Then they watched what happened: The eyeliner applied to the inner lash lines wore off ASAP—up to 30 percent more glitter moved into the eye when the product was applied to the inner eye area compared to makeup applied to the outer rim. Often, inner-rim liner came off within 10 minutes of application, with almost no product left on the lash line two hours later. (Even though researchers examined glitter liner, they expect similar results with solid colors.)
Because the eyeliner particles that flake or slide off your eyes get all up in your tear film, the results suggest that inner-rim lining—also known as tightlining—may be a bad idea for people who wear contacts or have dry or sensitive eyes—not to mention people who'd like their makeup to last all day. In the best-case scenarios, the makeup may cause discomfort, bind to your contact lenses, or temporarily blur your vision. But in the worst-case scenarios, it could set you up for an eye infection. If your eyeliner harbors bacteria, using it to line the inner rims of your eyes could be just as bad as shoving it into your eye. Ouch.
If you still love the look of inner-lined lids but feel a little paranoid about this study, save the look for special occasions. Before you apply it, always clean the tip of the eyeliner by sharpening it, or wiping down the tip of the pencil or brush with a tissue dipped in rubbing alcohol. And remember to toss the liner in your bag for regular touchups.
This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.