I recently listened to Andrew Huberman’s discussion on the science of hair growth and hair loss, and there was a lot in that conversation that immediately made me think about the lash industry.

Hair follicles. Growth cycles. Hormonal signalling. Blood supply. Stem cells. Growth factors. Medications. Follicular environments.

All of those concepts matter when we talk about hair.

But there is one very important distinction we need to make:

Eyelashes are hair fibres produced by follicles, so there are absolutely biological principles we can borrow from broader hair science.

But eyelash follicles have their own growth characteristics, their own anatomical environment and their own clinical considerations.

Eyelashes Have a Growth Cycle Too

Like other hairs on the body, eyelashes move through a biological cycle.

But eyelashes behave very differently from scalp hair.

Scalp hairs can remain actively growing for years. Eyelashes have a much shorter anagen phase, commonly reported at approximately four to ten weeks.

Lash growth itself is also relatively slow, with published literature reporting approximately 0.12–0.14 mm of growth per day.

This matters enormously when we start talking about lash-extension retention.

Natural Shedding Is Not Adhesive Failure

When we attach an extension to a natural eyelash, we are attaching that extension to a keratin fibre that has already emerged from the follicle.

We are not resetting the follicle’s biological clock.

If that natural eyelash is approaching the end of its cycle, the lash will eventually shed.

And when the natural lash sheds, the extension attached to it goes too.

That distinction is important.

In our industry we often use the word retention to describe several completely different events.

But these events should not all be grouped together.

Follicle Biology vs. Fibre Chemistry

This is one of the biggest distinctions I want lash artists to understand.

The follicle is living tissue.

The lash fibre that has emerged from the skin is primarily keratinized material.

Those are two completely different scientific environments.

This distinction matters every time we evaluate a lash product.

Lash cleanser, primer, mascara, lash-lift chemistry, conditioners and extension adhesive primarily interact with the existing lash fibre.

A product claiming to actually increase lash growth is making a fundamentally different claim because true growth requires an effect associated with the follicle and its biological cycle.

Does a Lash Serum Actually Grow Lashes?

This is where marketing language gets messy.

A product can make eyelashes appear healthier without necessarily stimulating follicular growth.

For example, conditioning ingredients may potentially:

• reduce friction
• improve flexibility
• decrease mechanical breakage
• coat the fibre
• improve shine or appearance
• help retain moisture within or around the fibre

If fewer lashes break, the lashes may eventually appear longer or fuller.

But that does not necessarily mean the follicle has been stimulated to produce hair faster.

Bimatoprost Shows Us What True Growth Modification Looks Like

One of the clearest examples of a compound capable of affecting eyelash growth is bimatoprost.

Bimatoprost is a prostaglandin analogue associated with increased eyelash prominence, including increases in lash length, thickness and pigmentation.

Its effects appear to involve alteration of the eyelash growth cycle, including changes associated with anagen.

That mechanism is completely different from applying a simple oil or conditioning polymer to the lash fibre.

And because pharmacologically active prostaglandin analogues can also be associated with unwanted periocular effects, this is exactly why we should treat the phrase “lash growth serum” with more scientific curiosity.

Ask what is actually inside it.

And What About DHT?

DHT is discussed heavily in conversations surrounding androgenetic scalp hair loss.

But this is another example of why we cannot automatically transfer scalp-hair mechanisms to eyelashes.

Eyelashes do not appear to demonstrate the same androgen-dependent behaviour seen in androgen-sensitive areas of scalp hair.

So saying:

would be an oversimplification.

Same molecule. Different tissue environment. Different follicular biology.

Scalp Treatments Should Not Become DIY Lash Treatments

Huberman also discusses interventions including minoxidil, caffeine, microneedling and other approaches used or investigated in scalp-hair growth.

Scientifically, those mechanisms are fascinating.

That does not mean lash artists should begin transferring scalp treatments to the eyelid.

The periocular area creates an entirely different safety environment.

Exposure to the ocular surface, eyelid skin, meibomian glands and surrounding tissues must all be considered.

What Does This Mean for Lash Extensions?

This biology gives lash artists a much better framework for understanding what we see during appointments.

1. Every lash is at a different point in its lifecycle.

Lash follicles cycle asynchronously. Your client does not wake up one morning and suddenly place every lash into anagen together.

That is why we see lashes of different lengths and developmental stages across the lash line.

2. Extension retention has a biological ceiling.

You can create an excellent adhesive bond and still lose that extension when the natural lash completes its biological cycle.

3. Attachment weight still matters.

The fact that lashes naturally shed does not give us permission to overload them.

Natural shedding and mechanical damage are not the same thing.

4. Lash condition and lash growth are not synonymous.

A lash can become brittle, mechanically damaged or chemically altered even when the follicle itself remains functional.

Conversely, a follicular growth issue may exist even when the remaining visible fibres appear structurally normal.

This Also Changes How We Talk About Retention

One of my biggest goals within lash education is getting artists away from treating retention as one single variable.

Retention is the outcome of multiple overlapping systems:

• natural lash growth and shedding
• surface cleanliness
• surface chemistry
• adhesive wetting
• cyanoacrylate polymerization
• environmental humidity and temperature
• attachment geometry
• extension weight
• mechanical stress
• client habits
• cosmetic and skincare exposure
• natural fibre condition

No primer can override biology.

No adhesive can stop a natural lash from eventually shedding.

And no single aftercare product determines the outcome of every lash set.

My Take as a Cosmetic Scientist and Lash Educator

What I love about conversations like this is that they force us to look underneath the service we perform every day.

Lash extensions are not simply about glue and extensions.

We are working with a biological fibre produced by living tissue, while simultaneously managing surface chemistry, polymer chemistry, mechanical forces and a very delicate periocular environment.

That is why I believe lash artists deserve more than simplified education.

We should understand enough biology to recognize normal shedding.

Enough chemistry to understand why an adhesive bond succeeds or fails.

Enough cosmetic science to evaluate the products we put around the eye.

And enough critical thinking to recognize when a scientific concept has been taken from one area of research and marketed as though it automatically applies to lashes.

Continue Reading

If you want to explore the science behind eyelash growth further, these are useful starting points:

• Eyelash growth and physiology — PubMed Central
• Biology and clinical considerations of eyelashes — PubMed Central
• Review of eyelash follicle biology — PubMed
• Andrew Huberman — The Science of Healthy Hair, Hair Loss and How to Regrow Hair

Educational content only. This article discusses cosmetic science and eyelash biology and is not intended to diagnose, treat or replace medical advice. Pharmacologically active lash-growth products and concerns involving eyelash loss, eyelid disease or ocular health should be discussed with an appropriate healthcare professional.