Why do we have eyebrows and eyelashes?

Eyebrows and eyelashes are one of the distinguishing features that make up our faces, and we pay a lot of attention to them, but the role of eyebrows and eyelashes, is more than just an adornment in reality.
The main goal of both is to protect the eyes, said Dr. Stephanie Mariono, a clinical spokeswoman for the American Academy of Ophthalmology. “Its goal is to create another layer of protection for the eyeball against anything, whether it’s liquid, solid, dust, debris, or insects,” she said.

Mariono told Live Science that eyebrows protect the eyes from substances such as sweat, dandruff and rain that fall on the face. The substance may pick up or absorb it, or its angle may direct it to the side of the face away from the eyes.”

Eyebrows serve some other functions. For example, eyebrows are essential for facial expression and communication with subtle emotions, and the brow ridge may have evolved to allow for more expressive brow movements, according to a 2018 virtual modeling study published in Nature Ecology & Evolution.

Eyelashes provide similar protection to the eyes, but they do it in a different way. “They are almost like facial hairs. They are long and sensitive. And when something touches them, it triggers a flicker response as a defense mechanism,” Mariono said. Without eyelashes, Mariono said, it would take longer to activate the flicker response, because the main trigger would be to see something coming into the eye. “But it does give you a little bit of a warning that something in the vicinity could actually hurt the eye,” she added.
Eyelashes can also pick up liquids, dust, and other eye irritants. They may help keep the eyes moist by reducing evaporation, according to a 2019 study in the Journal of the Royal Society Interface.

Some conditions can cause people to lose eyebrows or eyelashes. Alopecia, also known as patchy hair loss, can affect both. Sometimes, the eyelashes fall out for unknown reasons, or a person may pull out their eyelashes either because they are annoying or out of anxiety. In other cases, people with a condition known as trichotillomania have to pull their hair. An underactive thyroid can cause eyebrows to thin, and lupus can cause them to fall out.

And if you notice that your eyebrows or eyelashes are falling out or changing in another way, see a doctor, according to Mariono.

Source: Live Science