Every time we blink, air is funneled away from our eyes. Gone are dust and grit, thanks to our eyelashes.
In 2015, David L. Hue and colleagues from the Georgia Institute of Technology in Atlanta found that 22 mammalian species all have something in common: the length of their eyelashes is around one third of the width of their eyes. This list includes humans, snow leopards, camels, and the giant panda.
Using a wind tunnel and artificially created eye models, the team showed that this length is optimal for diverting air, keeping the surface of the eye moist, and stopping dust and other particles in the air from hitting our eyes.
As tempting as long lashes are, Hue and his colleagues showed that lashes that are longer than the optimum one-third ratio lose their ability to divert air, funneling dust particles straight into our eyes instead.
Eyelashes are similar to the hairs on the rest of our body. But while there is plenty of in-depth scientific knowledge about the locks that grace our heads and other forms of body hair, the eyelash hair follicle remains mysterious.
Finding human volunteers to study eyelash biology is quite difficult. For this reason, most existing knowledge comes from mouse and pig models.
What is known is that the upper eyelid has somewhere in the region of 90 to 160 eyelashes, neatly arranged in five or six rows. The lower eyelid is home to 75 to 80 lashes aligned in three or four rows.
The upper and lower eyelashes curl away from each other to stop them from getting tangled up when we blink.
Our genetic background determines how curly our eyelashes are. Individuals of Asian descent have eyelashes that are straighter and thicker but fewer in number than those with European ancestry.
Eyelashes are the darkest hairs on our bodies. They are also the last of our hairs to turn white.
When time catches up with our lashes
A study of 1,545 individuals aged between 1 and 90 years showed that the first white lashes appeared in participants in their 40s, but also that not everyone was affected.
Only 4 percent of study participants between the ages of 71 and 80 years showed whitening of greater than two thirds of their eyelashes.
Premature whitening can occur as a result of certain medical conditions, such as vitiligo. Although how and why this happens is not fully understood, scientists continue to search for effective ways of reversing this pigment loss.
Medical News Today previously reported on a study published in The FASEB Journal that used a modified enzyme called a pseudocatalase to reduce oxidative stress in the hair follicles.
In addition to diverting airflow, eyelashes are thought to play a significant role in communication between individuals. They are also an integral part of the human concept of beauty.
It is little surprise, then, that scientists are looking for ways to permanently enhance eyelash length and thickness.
In 2008, the United States Food and Drug Administration (FDA) approved an artificial version of prostaglandin F2alpha for treating eyelash deficiencies. Between February 2014 and January 2017, this product was prescribed to 271,829 U.S. adults.
This drug has been shown to increase the length, thickness, and color of eyelashes. However, it is not without side effects. These include itchy eyes, darkening of the skin on the eyelid, and inflammation of the eye.
But the results from Hue's study are worth bearing in mind. Longer lashes do not effectively divert airflow, potentially leaving us with an eye full of dust and grit.