| Down to a Science |

Why don’t your eyelashes grow as fast as your hair?

By Yael Zoldan | September 29, 2021

Eyelashes grow until they reach their optimum length. Then they fall out and new lashes grow

Hello kiddos,

This is Professor Mordy Maven, Thinker, Wonderer, and Figure-Outer of all things Science-ish. What that basically means is I try really hard to figure stuff out. I do the hard work so you don’t have to!

Now, you guys know how much I like to be helpful, right? Well, my brother’s hair was looking like a shaggy mess and given that his bar mitzvah is coming up, I knew how busy my mother was taking care of photographers, caterers, and stuff. She kept saying that she’s running around like a chicken without a head. (Interesting imagery!) I knew that there was no way she was going to have time to take him to the barber. And since I’ve always been good at cutting….

It only took a little convincing to get my brother to sit down on the stool in the bathroom and close his eyes. Then, I took out my scissors and gave him a haircut myself.

And guess what? It came out… wonderful! In fact, he looked so great that I felt confident enough to continue. I decided to give him a teeny, tiny trim… on his eyelashes.

When I was done, my brother looked shocked. People without eyelashes generally do. I felt kind of shocked, too. I might have gasped or something because my mother came in, and when she saw what I had done, she was less than pleased. At least, that’s what I deduced from the screaming, blubbering sounds that came out of her.

“Don’t worry, Ma!” I said encouragingly. “This kid’s hair grows like a bush, I’m sure his lashes will grow back in no time.”

Then my mother whirled around to look at me, and from the look on her face I decided to do the smart thing: move out of her way very, very quickly. I hurried to my room to do some research and what I found out wasn’t great. Because as it turns out, I might have been a tiny drop wrong about how fast eyelashes grow. Which led me to wonder,

Why don’t your eyelashes grow as fast as your hair?

First of all, you should know that most people have about 70 to 150 eyelashes on their top lid and between 30 to 100 hairs on their bottom lid. (I say most people, because my brother currently has none.) In any case, the job of eyelashes is to protect your eyes from foreign particles.

Okay, that’s what eyelashes are. But what makes them grow?

All the hair you’ve got grows in hair follicles and these follicles have three different phases of growth. The anagen phase is when the hair is actually growing. When the hair on your head is in the anagen phase, a hair strand will grow at a rate of about 15 centimeters per year. Around 85% of the hairs on your head are in the anagen phase at any given time. (See, even when you’re sitting around doing nothing, you’re actually doing something. You’re growing a bunch of hairs on your head!)

The catagen phase is when the hair follicle shrinks and detaches from its blood supply. It’s starting to get ready to fall out. Two weeks later comes the telogen or resting phase, where the hair just rests for a few months. Then it falls out, and a new hair starts to grow in the follicle, and the process starts all over again.

At any given time, around 10% to 15% of the hairs on your head are in the telogen phase. At this stage, the hair detaches from the follicle very easily. That’s why you sometimes see hairs falling out when you brush or wash your hair. (You already know my feelings about washing your hair too often!)

Your eyelashes go through the same stages: They grow until they reach their optimum length. Then they fall out and new lashes grow. The only difference is the timing. While the hair on your head stays in the anagen, or growth, phase for around six years, the hairs of your eyelashes are only in this stage for about 30 days. That’s why the hair on your head has a lot of time to grow really long and the hair of your eyelashes, not so much.

Based on the timing of the phases for eyelashes, I did some quick calculations and realized that it would only take about 150 days for my brother’s eyelashes to grow back.

When I learned this, I felt a lot better. I ran downstairs to give my mother the good news. “Don’t worry, Ma! In about five months he should be back to normal!” I shouted.

“But the bar mitzvah pictures are tomorrow!” my mother said. Then the wailing sound started even louder. I decided to leave the room again. I went up to the kitchen to explain what I had learned to my brother. He looked really shocked by the information. But honestly, it’s hard to tell because without eyelashes, he looks shocked all the time.

To sum it up, eyelashes do grow back. They just have to go through their phases. And as I told my mother, the important thing is to be patient. Now, I have to go get ready for the bar mitzvah. You’ll be able to identify my brother in the pictures really easily. He’s the one who looks stunned!