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Eyelash Growth Serum: What Actually Works?

Written by Dr Tom Walker | Last reviewed 12/05/2026

Eyelash growth serums are now one of the most searched and discussed categories in beauty. Many people, women and men, have tried at least one. Some see impressive results. Others see very little. The difference usually comes down to the active ingredient, the strength of the evidence, and whether the product is designed to genuinely stimulate growth, condition the lash hair, or protect lashes from avoidable damage.

This guide explains the main types of lash growth serum, including bimatoprost, prostaglandin analogue serums, peptide-based cosmetic serums, conditioning serums and protective serums. It is written for UK clients who want a clear, scientific explanation of what works, what is marketing, and how to choose safely.

At Opti Laboratories, we have specialised in eyelash and eyebrow growth since 2007. We are a group of doctors that are the UK eyelas experts. Our approach is evidence based: we separate clinically proven treatments from cosmetic products that may improve lash appearance or help protect the lashes, but are not proven to produce the same biological growth effect.

What is an eyelash growth serum?

An eyelash growth serum is a product to improve the appearance, length, density or condition of the eyelashes. The term is used very broadly which is why it can be confusing. Some eyelash serums are cosmetic conditioners. They coat and support the existing lash hair. Others contain ingredients that may influence the lash growth cycle. A smaller group, led by bimatoprost, has clinical evidence showing measurable eyelash growth. There is also a separate category of protective lash serums. These are not primarily designed to force new growth. Their role is to help protect the lashes you already have, especially from UV exposure, dryness, brittleness and mechanical damage.

Do lash growth serums work?

Some lash growth serums work, but not all work in the same way. The strongest evidence is for bimatoprost, which is the active ingredient associated with the original prescription eyelash growth treatment. Bimatoprost has been intensely studied and clinically proven to stimulate the eyelash growth cycle. Other cosmetic lash serums may improve lash appearance by conditioning the hair, reducing breakage or making lashes look glossier and healthier. That can still be useful, especially for damaged or dry lashes, but it is not the same as proven follicle-level growth stimulation. Protective serums have a different role again. They help to defend lashes and brows from avoidable damage, especially where the hair is exposed to sunlight, heat, cosmetic treatments, rubbing or dryness. For many clients, the best routine is not simply “growth” or “conditioning”, but a combination of growth support and protection.

Further reading on lash serum evidence

These articles explain how to judge lash growth serum claims and how bimatoprost compares with cosmetic eyelash serums.

The main types of eyelash serum

Most eyelash serums fall into one of five groups: bimatoprost, cosmetic prostaglandin analogue serums, peptide-based serums, conditioning serums and protective serums.

Type of serum How it is intended to work Strength of evidence Best suited to
Bimatoprost Acts on the eyelash growth cycle and can increase lash length, thickness and darkness. Strongest clinical evidence. People seeking a proven eyelash growth treatment.
Cosmetic prostaglandin analogue serums May influence lash growth through prostaglandin-like activity. Poor; often less transparent than bimatoprost. People wanting a cheap serum who understand the uncertainty.
Peptide serums Usually marketed to support lash condition, strength or appearance. Weak. Often self reported impression of improvement, not confirmed growth. People wanting to only support the hair rather than a growth led approach.
Conditioning serums Coat, moisturise or improve the feel and flexibility of existing lash hairs. Useful for cosmetic conditioning, but not equivalent to proven growth treatment. Dry, brittle or cosmetically damaged lashes.
Protective serums Help protect existing lashes from environmental and mechanical stress, including UV exposure, dryness, friction and brittleness. In addition, they also condition the hair. Useful when supported by appropriate protective ingredients and testing, but should be judged separately from growth-stimulating treatments. People using lash growth treatment, lash lifts, lash tints, extensions, or anyone trying to protect fragile lashes from avoidable damage.
Real results from clients of Opti Laboratories
A "before and after" client picture
side by side picture of results after 2 months
A "before and after" client picture after 12 weeks

Bimatoprost: the best evidence for lash growth

Bimatoprost is the most important active ingredient in the eyelash growth category because it has clinical evidence behind it. It was originally developed in ophthalmology as a glaucoma treatment and became known for its effect on eyelash growth.

When used correctly along the lash line bimatoprost will help lashes grow longer, thicker and darker. It works by stimulating the eyelash growth cycle, particularly the growth phase. This is different from simply conditioning the visible lash hair.

For UK clients, it is important to understand that bimatoprost is not the same type of product as an ordinary cosmetic lash serum. This is a prescription strength lash growth treatment that should be supplied only through an appropriate doctor led route like Opti Laboratories, with proper screening and clear instructions.

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Further reading on bimatoprost

These articles explain bimatoprost, how it works, expected results and how it compares with other lash serum options.

Cosmetic prostaglandin lash serums

Some cosmetic lash serums include prostaglandin analogues or other prostaglandin like ingredients. These products sit in a more complicated area. They may produce visible lash growth in some users, but the evidence, regulation, labelling and side-effect profile can be less clear than with a properly supplied bimatoprost treatment.

In fact, these compounds have been deemed unsafe for cosmetic use in the European Union.

The issue is not that every cosmetic prostaglandin serum is ineffective. The issue is that clients are often not given enough information to understand what they are using, how it works, or why side effects may occur.

Peptide and conditioning lash serums

Peptide and conditioning lash serums are usually positioned as gentler cosmetic products. They may contain peptides, panthenol, hyaluronic acid, amino acids, botanical extracts or other conditioning ingredients.

These products may help lashes look healthier if the main problem is dryness, brittleness or breakage. They may also improve the feel and cosmetic appearance of the lash hair. However, they should not be assumed to produce the same result as bimatoprost.

A good conditioning serum can still have a role, especially as part of a lash-care routine, but it will not cause the eyelashes to noticeably grow. They are carefully worded, often talking about “longer looking lashes”. It is simply important to separate lash conditioning from true lash growth stimulation.

eyelash serums available in 2026

Protective lash serums

Protective lash serums are a separate and important category. They are not primarily designed to stimulate the follicle into stronger growth. Their role is to protect the lash hair that is already present.

This matters because eyelashes and eyebrows are exposed to daily stress. UV light, heat, dryness, friction, rubbing, cleansing, mascara removal, lash lifts, lash tints and extensions can all affect the condition of the hair shaft. If the lash hair becomes dry, brittle or mechanically weakened, it may break or shed before it has reached its best visible length.

Protection is particularly important in the case of cosmetic enhancements like eyelash extensions, lifts + tints, brow lamination, microblading and others. UV exposure will degrade these treatments and a protective serum can prolong the results, particularly during the summer months.

A protective serum is therefore best thought of as part of a preservation strategy. It helps protect the results you already have, and it may be particularly useful alongside a growth treatment such as bimatoprost, where the aim is not only to encourage better growth but also to help preserve the new lash length and quality.

Opti Laboratories developed the worlds first Sun Protect Serum for this reason. It is positioned as a lash and brow protective serum, helping to protect delicate hairs from environmental stress, including UV exposure. It is not intended to replace bimatoprost as a growth treatment. It plays a complementary role: growth support from the active treatment, protection and conditioning from the protective serum. 

My biggest flex right now is using the @Opti.labs Sun protect serum.
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Opti Laboratories Sun Protect Serum

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Further reading on UV protection and lash damage

These articles explain how UV exposure, melanin and environmental stress can affect eyelashes and eyebrows, and why protection may help preserve lash quality.

How to choose the best lash growth serum

The best lash growth serum depends on what you are trying to achieve. If your goal is proven eyelash growth then the evidence points most strongly and clearly towards bimatoprost. There is no equal. If your goal is lash conditioning then a cosmetic serum may be enough. If your concern is damage from UV light, or want to protect extensions, a lash lift or your brow lamination, then a protective serum may be more relevant.

Before choosing, ask five questions:

  • Is this product designed to stimulate growth, condition the lash hair, or protect existing lashes?
  • What is the active ingredient?
  • Is there clinical evidence for the type of result being claimed?
  • Are the side effects and limitations clearly explained?
  • Who is behind the product? Are they experts?

Be cautious with vague claims such as “longer-looking lashes” or “supports natural lash potential” if the product does not clearly explain its active ingredient or evidence base.

Side effects and safety

Lash serums are applied close to the eye so safety matters. Potential problems include irritation, redness, itching, dryness, skin darkening around the application site, unwanted hair growth if the serum spreads, and changes in the appearance of the eyelid area.

Bimatoprost and prostaglandin-type products deserve particular care because they can produce biological effects. They should be used as directed and not applied excessively. More product does not mean faster or better results.

Opti Laboratories are the UK experts in eyelash growth with decades of experience. We can help guide you to minimise the chance of experiencing any problems. We have clients that have been with us for close to 20 years that have had no side effects, and we have not had any clients that have had a serious side effect

Protective and conditioning serums may be gentler but they still need careful formulation because they are used near the eye. If a product stings, irritates the eyelids or worsens redness, it should be stopped and reviewed.

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How long results take

Lash growth takes time because eyelashes grow in cycles. With active growth treatments, early changes may be noticed after two or three weeks but fuller results usually require consistent use over a longer period.

Conditioning and protective serums can sometimes improve the feel or appearance of the lashes sooner, because they act on the surface of the hair rather than waiting for new hair growth.

A realistic expectation is important. Lashes do not grow overnight. They need time to move through the growth cycle. If an active growth product is stopped, the effect will gradually reduce as treated lashes shed naturally and are replaced by new hairs.

What to do if a lash serum did not work

If a lash serum did not work, the first step is to identify what type of serum it was. Many products sold as “lash growth serums” are mainly conditioning products. They may improve lash quality but may not produce dramatic growth.

The second issue is time. Lash growth takes weeks to months, and inconsistent use can reduce the chance of seeing a clear result.

The third issue is the underlying cause. If eyelashes are thinning because of thyroid disease, chemotherapy, medication, rubbing, eyelash extensions or inflammation around the eyelids, the best approach may require more than simply adding a serum.

Further reading on causes of eyelash and eyebrow thinning

These articles explain common reasons lashes and brows may thin, shed or become more fragile.

The UK eyelash experts

Opti Laboratories offer evidence based treatments that help you grow your eyelashes longer, thicker and darker. We carry out our own cutting edge research to make sure that we remain the experts in our area. 

Dr Tom Walker is one of the founders of Opti Laboratories, the successor to Mylash which he founded in 2007. He graduated from the University of Glasgow with a degree’s in medicine and anatomy. His work has been featured in publications including The Times newspaper and Vogue magazine. He has a passion for bringing innovative and evidence based treatments to the market. The eyelash and eyebrow growth treatment he introduced is the only clinically proven growth treatment available.

“I lost eyelashes on chemotherapy and was recommended the lash serum by a friend who had also had chemo. My eyelashes have genuinely grown back even longer than they were before they fell out and everyone has been complimenting me on them. They are noticeably long and thick looking. Really highly recommend to anyone who has lost lashes.”

Sophie C, verified buyer

I had chemotherapy last year and have been using the OptiLaboratories Lash Growth Treatment ever since. I can honestly say it’s one of the most incredible products I’ve ever used.

I’ll admit, my expectations were low—we’ve all tried products that promise everything and deliver very little. But this completely exceeded anything I imagined.

My lashes had been significantly affected by chemo and ongoing medication, but since using this treatment, they’ve grown stronger and healthier over time. I now have noticeably longer, fuller lashes, and it’s made such a difference to how I feel.

For the first time in a long time, I feel genuinely confident again”

Claire B, verified buyer

“Have been using the product for many months and it works like magic for eyelash growth – gentle on eyes and surrounding skin. I’ve suggested it to friends and they’re using it as well. The results speak for themselves.”

Sonia P, verified buyer

FAQ: Eyelash growth serum

What is the best eyelash growth serum?

The best eyelash growth serum depends on whether you want proven growth or cosmetic conditioning. For proven eyelash growth then bimatoprost, found in the Opti Laboratories Lash Growth Treatment, has the strongest clinical evidence. Peptide and conditioning serums may improve lash appearance, but they should not be treated as equivalent to bimatoprost.

Do eyelash growth serums really work?

Some eyelash growth serums really work, but the result depends on the active ingredient. Bimatoprost can increase eyelash length, thickness and darkness. Many cosmetic serums mainly condition the lashes and may make them look healthier without producing the same growth effect.

What is the difference between an eyelash serum and an eyelash growth serum?

An eyelash serum may simply condition or moisturise the lashes. An eyelash growth serum should contain an active ingredient intended to influence the lash growth cycle. The terms are often used loosely, so it is important to check the ingredient and evidence.

Is bimatoprost better than cosmetic lash serums?

Bimatoprost has stronger clinical evidence for eyelash growth than ordinary cosmetic lash serums. Cosmetic serums may still be useful for conditioning or reducing breakage, but they are not usually supported by the same level of growth evidence.

How long does eyelash growth serum take to work?

Eyelash growth serum usually takes several weeks to show early changes, with fuller results taking longer because eyelashes grow in cycles. Consistent use is more important than applying extra product.

What happens when I stop using eyelash growth serum?

When you stop using an active eyelash growth serum, the effect gradually reduces as treated lashes naturally shed and are replaced by new lashes. The eyelashes normally return towards their previous appearance over time.

Can eyelash growth serum cause side effects?

Yes, eyelash growth serum can cause side effects, especially if it contains bimatoprost or a prostaglandin-type ingredient. Possible side effects include irritation, redness, itching, dryness, skin darkening around the application area and unwanted hair growth if the product spreads.

Can I use eyelash growth serum with eyelash extensions?

Some eyelash growth serums may be used by people who wear eyelash extensions, but the formula and application method matter. Avoid oily products if your lash technician advises against them, and apply any serum carefully so it does not interfere with the extension bond.

Why did my lash serum not work?

Your lash serum may not have worked because it was mainly a conditioning serum, because it was not used consistently for long enough, or because there is an underlying cause of lash thinning such as thyroid disease, medication, inflammation, rubbing or previous cosmetic damage.