Why do we have eyelashes?

Despite several theories, eyelashes' 'function has long remained a mystery'.¹ Some biologists believe that eyelashes act as whisker-like sensors. Others speculate that, in humans at least, eyelashes help communicate expressions and draw attention to the eyes,¹ an attribute cosmetic manufacturers have exploited since Eugene Rimmel invented mascara in 1840.

Eyelashes undoubtedly protect eyes from dust and airborne particles. Children with allergies have eyelashes that are 10% longer and denser than those without. However, how eyelashes protect the eyes is another mystery.¹ So, researchers modelled the eyelashes of 22 species of mammals as diverse as the Amur hedgehog, nine-banded armadillo, panda, giraffe, chimpanzee and humans. In each species, the length of the eyelashes is roughly one-third the eye's width.¹