Eyelashes look decorative.
They also do practical work.
Their main job is helping protect the eyes.
Lashes catch some debris
Dust, tiny particles, and other material moving toward the eye can hit the lashes first.
The lashes do not form a perfect filter.
They simply add another barrier before something reaches the sensitive surface of the eye.
They help trigger blinking
Eyelash follicles are sensitive.
Touch a lash and the nervous system can trigger a blink.
That closes the eyelids quickly and helps protect the eye.
It is an extremely simple warning system.
Something touched the perimeter.
Shut the doors.
Why are eyelashes curved outward?
The shape helps keep them away from the eye surface while still placing them where they can intercept particles and airflow.
Lashes that grow inward can actually irritate the eye, which shows how important their direction is.
Do lashes help with airflow too?
Research suggests eyelashes can influence airflow around the eye.
The right length may help reduce how much air and dust reach the eye surface.
That could also help slow evaporation of the tear film.
How does this connect with eyebrows?
Eyebrows help protect the eyes too, especially by redirecting sweat and water.
Eyelashes protect the eye from the front.
Eyebrows help manage what comes down from above.
The face has more engineering than it gets credit for.
Why do eyelashes fall out?
Like other hairs, eyelashes grow in cycles.
Old lashes eventually shed and are replaced.
Losing an occasional lash is normal.
So eyelashes are not just decorative trim around the eye.
They are tiny security guards with a very simple alarm system:
Something touched me.
Close the eye.
And that’s the short explanation.
Related explanations: Why do we have eyebrows?, Why do your eyes water when you yawn?, and Why do cats have whiskers?