Why Do Some People Have Genetically Long Eyelashes?

Have you ever wondered why some people have naturally long eyelashes and some people don’t? Have you ever wondered if genetics caused eyelash length? Genetics does appear to play a part. How? Well, in the following post that’s exactly what we are going to discuss.

We are going to give you a fascinating insight into the genetics surrounding eyelash length. After reading, you may want to grab yourself a pair of lash extensions to give that appearance of long eyelashes.

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Although we all have our own opinion as to what constitutes long eyelashes and what doesn’t, there is a length that’s officially considered as long eyelashes. That is 12mm and it is often known as eyelash trichomegaly. So, it’s best to start there.

What Exactly is Eyelash Trichomegaly?

Trichomegaly is the name given to eyelashes longer than 8mm in the peripheral section and 12mm in the central section. There are a variety of causes of eyelash trichomegaly, including environmental factors, and yes, genetic inheritance.

Congenital Trichomegaly

As suggested by the name, congenital trichomegaly occurs when someone has longer than normal eyelashes because of either a syndrome or disorder they’ve had since they were born.

Two, in particular, Cornelia de Lange and Oliver-McFarlane syndrome result in the sufferer having extremely long eyelashes, more so than normal. Although, it doesn’t necessarily follow that someone with long eyelashes has one of these conditions. They have various other symptoms as well as long eyelashes. 

It’s very rare to have just extra-long eyelashes with no additional symptoms… it does happen though!

What About Familial Trichomegaly?

Sometimes, on those rare occasions, there are no additional symptoms and people in the same family have abnormally long eyelashes as a trait. Scientists, like many of us reading this, are fascinated by long eyelashes and their origins.

To try and understand what was going on better, they took DNA samples of people with trichomegaly eyelashes and compared their samples with the DNA of family members with shorter eyelashes.

What did they discover? The people with long eyelashes had mutated forms of the FGF5 gene.

So, what is FGF5 and What Does it Have to Do with Eyelash Length?

The abbreviation FGF5 means Fibroblast Growth Factor 5 and this is what’s responsible for producing the protein that blocks out more hair growth than necessary. The protein and the gene both share the same name so don’t get confused. Isn’t science a little confusing sometimes? 

The thought is that the mutated gene is unable to produce the protein and that’s why the hair can grow much longer, especially the eyelashes.

Mutated?

Now, we all have two unique copies of the gene, from both our parents respectively. Generally, the two copies are working hard to make the protein. However, what happens if you have two broken or mutated copies of the gene? Trichomegaly, that’s what!

What, though, if there is one normal FGF5 gene and one mutated version? Well, it seems you only need one fully functioning ordinary gene to block out unnatural hair growth. As such, it’s what’s known as a recessive trait, as your body needs two mutated gene copies to gain long eyelashes.

How, then, is it Inherited?

There is only one way you can possibly get two FGF5 mutations and that’s if you get a mutated version of the gene from each of your parents – something that is thought to be quite rare.

What about Trichomegaly and Drugs?

You may recall we noted earlier that trichomegaly was caused by genetics or drugs. So, what drugs can cause eyelash trichomegaly? Well, for one there is Latanoprost. This is a medication used in the treatment of glaucoma.

Glaucoma is a serious condition that affects the optic nerve of the eye, damaging it through increased pressure, also known as intraocular pressure. As the optic nerve is the part of the eye that sends images to your brain, as glaucoma worsens, your eyesight diminishes. 

Back to Latanoprost, as well as treating glaucoma, it also stimulates cells of hair follicles, extending their growth cycle resulting in, you’ve guessed it, longer lashes! Another drug, called Erlotinib, used in the treatment of lung cancer, also appears to cause eyelash trichomegaly, through stimulation of the hair follicles.

So, now you know. Whenever you see someone with exceptionally long eyelashes, that are not fakes, it could be the sign of a specific congenital condition they suffer from, medication they are on for a serious medical condition or because their parents had long eyelashes too.