The next time you pick up a pencil eyeliner, please consider that its particles can move into the eye and cause vision trouble.
The findings published in the journal Eye and Contact Lens Science and Clinical Practice emphasised that eyeliner can alter the tear film - the thin coating protecting the eye and add to discomfort.
"We noticed that the makeup migration happened quicker and was greater when eyeliner was put on the inner lid margin," said Alison Ng from the University of Waterloo in Candada.
The researchers used video recordings to observe and compare the amount of eyeliner particles that migrated into the tear film after applying makeup in different styles.
Each participant wore glitter eyeliner outside the lash line, and then on the inner lid area closer to the eye, or along the waterline.
The scientists found that within five minutes, between 15 and 30 percent more particles moved into the eye's tear film when participants applied eyeliner to the inside of the lash line, compared to outside it.
The makeup also moved more quickly into the eye when eyeliner was applied inside the lash line.
Eyeliner ingredients commonly include waxes, oils, silicones and natural gums to help eyeliner stick to eyelids and last for prolonged periods.
Makeup that enters the tear film may cause discomfort for those with sensitive or dry eyes and also for those who wear contact lenses.
"If you thoroughly sharpen your pencil eyeliner before each application and get rid of the stuff that's stuck to the end, you will have a fresh tip which can help prevent infection," Ng pointed out.