Researchers at the Georgia Institute for Technology measured the lashes of a variety of animals, from humans to giraffes, and discovered something curious and fascinating: in 22 of the species (including us), our lash length is exactly one-third the width of our eyes. And there is a good reason for that—that is the perfect ratio to keep the eyes from drying out.
So wouldn’t longer lashes be even better, you ask? Actually, no. According to the study, anything longer (including false eyelashes or eyelash extensions) actually started funneling more air and dust into the eye and sped up evaporation.
But it’s really length, not thickness, that is bad for the eye. So if you love fake eyelashes, get the short kind.