How do lash serums work and are they safe?

Everything you need to know about lash serums – from how they work to how safe they are

27th May 2024 | Author: Victoria Woollaston-Webber

Lash serums promise to be the solution to your short lash woes but not all are created equal. Here’s everything you need to know about how they work and how safe they are

Lash growth serums have surged in popularity in recent months with people looking to enhance their own lashes, rather than paying for expensive beauty treatments and eyelash extensions.

What’s more, lash growth serums promise to improve the health and condition of your lashes whereas eyelash extensions have been linked with making them weaker.

However, with this rise in popularity there’s also been a rise in concerns and debates about how well they work and how safe they are.

To help you understand more about this debate, we’ve explained how the best eyelash serums work, plus what to look for, what to avoid.

How do lash serums work?

Olaplex LashBond Building Serum launch resultsOlaplex

Lash serums are designed to enhance the appearance of eyelashes by applying nourishing ingredients and active compounds directly to the lash hair follicles.

There are a number of ways different lash serums work. Some ingredients and techniques are more effective than others while some are more controversial than others. However, most lash serums work by creating a healthy environment for eyelashes to grow as strong and thick as possible. The most common ingredients include:

  • Prostaglandin Analogs: These are potent ingredients found in certain FDA-approved serums, such as bimatoprost in Latisse. They mimic natural fatty acids and promise to extend the anagen phase of lash growth, leading to thicker, stronger, longer-lasting lashes.
  • Peptides: These amino acid chains are believed to strengthen hair follicles by reinforcing the keratin structures that comprise each eyelash, potentially enhancing the lashes’ durability and length.
  • Vitamins and Oils: Ingredients like biotin, panthenol, and castor oil nourish and condition the lashes, although their direct impact on growth is less substantiated compared to prostaglandin analogs.

Prostaglandin Analogs

Prostaglandins are hormone-like fatty acids that occur naturally in our body. They’re found in almost every tissue throughout the body and, instead of being produced from glands like hormones are, they’re produced in various tissues as needed.

They have a range of effects depending on where they are produced and what receptors they bind to in the body. In the cases of eyelashes, PGAs work to prolong the lash’s anagen phase (growth) phase. By extending this growth period, lashes have more time to grow longer and thicker before entering the shedding phase.

The prostaglandins analogs found in lash serums are synthetic versions of these naturally-occurring prostaglandins.

Studies have shown their effectiveness in increasing lash length, thickness, and darkness. Yet they’ve also been linked with side effects such as eyelid darkening, irritation, fat loss around the eye, and in rare cases they have even been blamed for changing the colour of a person’s iris.


What are peptides and how do peptides for skin workGetty Images/iStockphoto

As you can read in our guide to peptides in skincare, peptides are short chains of amino acids which are the building blocks of protein. In lash serums, peptides are thought to target the hair follicle, where lashes grow, to provide them with what they need to grow thick and strong.

Some peptides can encourage the follicle to produce more lash cells, while others interact with keratin, the protein that makes up hair, to make lashes more resilient and less prone to breakage.

Research on the effectiveness of peptides for lash growth is ongoing. It’s not as conclusive as with PGAs but they’ve also not been linked to some of the same issues seen in studies of prostaglandins. As a result, more studies are needed to fully understand their impact.

Vitamins and oils

Every function of the human body can benefit from vitamins and minerals and your eyelashes are no different. By adding vitamins like biotin and panthenol to lash serums, they can help promote hair health as they grow, while also nourishing and conditioning the lashes, improving their overall appearance.

Elsewhere, castor oil has been linked with helping promote healthy hair on the head so promises to play a similar role in boosting eyelash growth. If anything, the oils can help moisturise the lashes and skin around them, and add shine.

However, its impact on actual growth is unclear. There’s limited scientific evidence to directly link vitamins and oils to lash growth and their main benefit seems to be lash conditioning. As a result, they may not boost lash growth, per se, but they can make the lashes that do come through look and feel as healthy and strong as possible.

How long do eyelashes take to grow?

How long do eyelashes take to grow and do they grow back?Shutterstock

To understand how eyelash serums work, it’s worth explaining how eyelashes grow.

Eyelashes, like other hair on the body, grow in a cycle that includes three key phases – Growth > Transition > Rest.

  • Anagen (Growth) Phase: This is the active growth phase where eyelashes are continuously growing. Each lash will grow to a certain length over about 30 to 45 days. The length they grow to largely depends on your genetics, and follicle size and shape.
  • Catagen (Transition) Phase: This phase lasts two to three weeks. During this phase, the hair growth stops and the hair follicle shrinks. If an eyelash falls out during this phase, it won’t begin growing back until the phase ends.
  • Telogen (Resting) Phase: The eyelashes and hair follicles then rest for ~100 days before the eyelash falls out and a new lash begins to grow in its place. This is a natural and regular part of the hair cycle.

This means it can take a staggering 23 weeks for your eyelashes to grow, although most people’s cycle is around 12-16 weeks. As a result, you may not seen any noticeable differences from using lash growth serums until your eyelashes have gone through this cycle.

Understanding this cycle is crucial because lash serums mainly work to extend the anagen or growth phase. This helps them grow longer and thicker before transitioning to the shedding phases. If you continue to use the serum, the lashes that come through during the telogen phase are also more likely to be stronger and less likely to shed early.

Are lash serums safe?

To be sold in the EU, lash serums like many other cosmetics are governed by the EU Cosmetic Regulation (EC No. 1223/2009). This regulation specifically governs the sale and distribution of cosmetic products across all EU member states. To be deemed safe, products have to tick the following boxes:

  • Safety assessment: Before an eyelash serum can be marketed in the EU, it must go through a safety assessment, by a qualified professional such as a cosmetic chemist or a toxicologist, who will compile a safety report.
  • Labelling: The product must be properly labelled according to EU regulations. Labels must include the list of ingredients (using INCI names), the name and address of the responsible person, the country of origin, the batch number, the expiration date or PAO (Period After Opening), and how to use.
  • Evidence and substantiation: Any claims made about the product, such as “promotes lash growth” or “increases lash volume,” has to be substantiated. This sometimes includes clinical trials, user studies, or other data. Note that a small test on a consumer sample counts as substantiation so always check the asterisks to see how the evidence was compiled.
  • Cruelty-free: Since March 2013, animal testing for cosmetic products and their ingredients is banned in the EU. This includes products made in the EU as well as those imported from outside the EU.

As a result, if a lash serum is sold in the EU, and by association the UK, it’s considered safe to use. However, some people can be allergic to the ingredients, or the serum can cause irritation, redness and soreness, especially if you have sensitive skin.

More serious side effects are rare but can happen, especially with serums that contain prostaglandin analogs.

In summary, lash serums can be a good way to achieve fuller, longer eyelashes, but you have to use them carefully and responsibly. Especially because they’re applied close to your sensitive eye area but as the science around some of the ingredients is still under debate, it’s worth getting clued up about the possible side effects before use.

Do eyelash serums actually work?

Before and after Olaplex LashBond serum results on short lashes without makeupmamabella | mamabella

These images show the Before and after Olaplex LashBond serum results on our short lashes without makeup

In our experience, yes lash serums actually work. But the results can vary.

We have very short, straight lashes. Using Glow For It’s lash serum made very little difference to our lashes, yet Olaplex’s Lash Bond brought about a lash transformation.

It should be noted that the effects only last all the time you’re regularly applying the serum.

If you stop, or decrease the frequency your lashes will start to grow in the way they used to.

What to look for – and avoid – when buying lash serums

Here are a few things to keep in mind when shopping for lash growth serums:

  • Check the ingredients: Avoid serums with ingredients that have been linked with causing allergic reactions or irritation, especially if you have sensitive skin. Be cautious of products with prostaglandin analogs if you are concerned about the more serious side effects they can cause. The INCI Decoder website is a good place to start, but bear in mind it’s the overall formula that determines if a product causes a reaction, not the individual ingredients.
  • Always do a patch test: Before you start using any new lash serum, or skin product for that matter, it’s worth doing a patch test. Apply a small amount of the serum to your inner arm and wait 48 hours to see if there’s a reaction.
  • Follow the instructions: Use the serum according to the product instructions. Most serums suggest applying them once a day, or two times a day at a push. Don’t assume that using more is better — it won’t make your lashes grow faster or fuller and could actually increase the risk of side effects.
  • Keep an eye on any changes (excuse the pun): Pay attention to how your body, and particularly the skin and fat around your eye, reacts after you start using the serum. If you notice irritation or other changes, stop using the product and seek expert help if needed.
  • Read reviews: This is a good rule of thumb generally but always check the reviews of products before buying. Ideally from a range of customers. Influencers are often paid for their opinion and this can muddy the water a little. As a result it’s worth checking reviews and opinions from a couple of places to get a more informed, accurate viewpoint.
  • Check the expiration date: Make sure the product is not past its expiration date, which can lead to reduced effectiveness and increased risk of irritation.

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