TUESDAY, April 7, 2015 (HealthDay News) -- Applying pencil eyeliner to the inner eyelid increases the risk that particles will get into the eye and cause vision problems, a new study warns.
Volunteers first applied glitter eyeliner outside the lash line and then on the inner lid closer to the eye. Within five minutes, 15 percent to 30 percent more eyeliner particles moved into the eye's tear film -- the thin coating protecting the eye -- when eyeliner was applied to the inner eyelid, compared to outside the lash line.
Particles also moved more quickly into the eye itself when eyeliner was applied inside the lash line, according to study leader Alison Ng, of the Center for Contact Lens Research at the University of Waterloo in Canada.
Eyeliner particles in the tear film may cause discomfort for people with sensitive or dry eyes, and can also adhere to contact lenses and accumulate if used for more than one day, Ng explained. That can lead to complications such as irritation and redness, the presence of harmful bacteria, and even eye infections or blurred vision.
The study was published recently in the journal Eye and Contact Lens Science and Clinical Practice.
Previous research has also shown that old eye makeup can harbor bacteria, Ng noted.
"If you thoroughly sharpen your pencil eyeliner before each application and get rid of the stuff that's stuck to the end, you'll have a fresh tip which can help prevent infection," Ng said in a university news release.
"With twist-up eyeliner, cut some off the end before each use," Ng added. "And always make sure to fully remove eye makeup before bed."
The U.S. National Library of Medicine has more about cosmetics.