Do Eyelash and Eyebrow Serums Actually Work? The Ingredient That Decides, the Risks, and My Results with Obagi Nu-Cil

Last updated: 27 October 2026

I have always had reasonable eyelashes, but I cannot tolerate false lashes for more than an hour and I disliked the lash lift process enough to never repeat it. So when lash and brow serums became something half my patients in Hale and Altrincham were asking about, I did what I do with every product I am asked to recommend: I read the ingredients and the evidence, and then I tested it on myself for twelve weeks.

The short answer is that the serums that visibly work mostly share one family of ingredients, and once you know which family, you know both why they work and what you need to be careful about. This article explains that, sets out the evidence and the side effects without flinching, and then gives you my own results with Obagi Nu-Cil, a serum I stock at the clinic and which, I should say plainly at the outset, belongs to that ingredient family.

In this article:

• How do lash and brow serums work?
• The ingredient that decides: prostaglandin analogues
• What the clinical evidence shows
• What is actually in Obagi Nu-Cil?
• Side effects and who should not use a prostaglandin serum
• What the regulators say
• My 12-week results with Nu-Cil
• How to use a lash serum safely
• Frequently asked questions

How do lash and brow serums work?

Every lash and brow hair moves through the same three-phase cycle: anagen, the growth phase, which for an eyelash lasts only a few weeks; catagen, a short transition; and telogen, the resting phase before the hair sheds and a new one begins. Lashes are short because anagen is short. A serum can only do three things: keep more hairs in anagen for longer, make each hair thicker and darker as it grows, or condition the hair shaft so fewer break off. The first two change the hair. The third changes how it looks.

Type of serum	What it does	What to expect
Conditioning serums peptides, biotin, panthenol, hyaluronic acid, castor oil	Coat and condition the hair shaft, reduce breakage and shedding from mechanical damage	Shinier, better-behaved lashes that look slightly fuller because fewer snap off. No real change in length or number. No meaningful side effects
Prostaglandin-analogue serums any ingredient ending in "-prost" or "-prostenate", including isopropyl cloprostenate, ethyl tafluprostamide, dehydrolatanoprost	Act on the follicle itself, extending the growth phase and increasing hair thickness and pigment	Visibly longer, thicker, darker lashes within 8 to 16 weeks. The only kind with real evidence of growth. Carries a specific set of side effects
Prescription bimatoprost the glaucoma drug, licensed for lash growth in the US and used off-licence in the UK	The same mechanism at a defined pharmaceutical dose, under medical supervision	The strongest and best-documented results, with the same side-effect profile

Most serums on the shelf are a mix: conditioning ingredients on the front of the box, and a prostaglandin analogue somewhere in the ingredient list. The conditioning ingredients make the lashes look nice. The prostaglandin makes them grow.

The ingredient that decides: prostaglandin analogues

The story begins with glaucoma. Patients using prostaglandin eye drops such as latanoprost and bimatoprost to lower eye pressure noticed, as a side effect, that their lashes grew longer, thicker and darker. The drug company turned the side effect into a licensed product, and the cosmetics industry followed with chemical cousins of the same molecules at cosmetic concentrations, which is how a pharmacologically active glaucoma derivative came to be sold next to mascara.

These analogues are potent at very low concentrations, which is the point, and they are applied millimetres from the eye, which is the problem. The European Scientific Committee on Consumer Safety, asked to assess them, described the class this way:

"Prostaglandins and synthetic analogues are widely known to be potent pharmacologically active substances."
Scientific Committee on Consumer Safety, Opinion SCCS/1635/21, 2022

None of this means the serums are dangerous for everyone. It means they are active products with real effects and real side effects, and should be chosen and used that way, rather than as a cosmetic conditioner.

What the clinical evidence shows

For prescription bimatoprost, the evidence is excellent and gives us the benchmark for what a prostaglandin serum can do.

Measure at 16 weeks	Bimatoprost 0.03%	Placebo
Visible improvement on the investigator's global scale	78% of patients	18% of patients
Lash length	Up about 25%	Minimal change
Lash thickness and fullness	Up about 106%	No significant change
Lash darkness	Up about 18%	No significant change

That was a randomised, double-blind, placebo-controlled trial of 278 adults published in the Journal of the American Academy of Dermatology in 2012, funded by the manufacturer. A smaller randomised trial found the same drug improved sparse eyebrows. The effect wears off over two to three months when you stop.

For the cosmetic analogues, including the one in Nu-Cil, the evidence is thinner and comes from manufacturers rather than independent trials. Obagi reports a 16-week double-blind study in which 93% of participants said their lashes showed visible improvement and 89% said they looked thicker and more densely packed, and a 12-week brow study with high response rates; both are data on file with the company. Given the shared mechanism, results of that order are plausible, but they are the brand's figures, not peer-reviewed ones.

For pure conditioning serums, there is no trial showing lash growth. They can make lashes look better. They do not make more of them.

What is actually in Obagi Nu-Cil?

I stock Nu-Cil and I use it, so this section is written against my own commercial interest, which is the only way it is worth writing.

Obagi describes Nu-Cil's active complex, NouriPlex, as a blend of biotin, panthenol, sodium hyaluronate and "a proprietary lipid compound". The full ingredient list names that compound: dehydrolatanoprost, listed second after water. Dehydrolatanoprost is a derivative of latanoprost, the glaucoma drug, and it is a prostaglandin analogue. In other words, Nu-Cil is a prostaglandin-analogue lash serum, which is why it works and why the warnings on its packaging read the way they do.

Ingredient	What it is	What it does
Dehydrolatanoprost	A prostaglandin analogue related to the glaucoma drug latanoprost	The active ingredient. Extends the growth phase and increases thickness and pigment. Responsible for the results and for the side-effect profile
Biotin	Vitamin B7	Supports keratin; conditioning benefit only when applied topically
Panthenol	Vitamin B5	Conditions and softens the hair shaft, improves shine
Sodium hyaluronate	A form of hyaluronic acid	Hydrates the lash line and makes hairs look plumper

I say this not to put you off the product, which gave me a good result, but because a doctor recommending it should tell you what it is. If you have read elsewhere, including in an earlier version of this article, that Nu-Cil works by conditioning alone, that was wrong, and I have corrected it. [If the UK-supplied formula differs from the US ingredient list, amend this section accordingly before publishing.]

Side effects and who should not use a prostaglandin serum

This applies to every lash and brow serum containing a prostaglandin analogue, Nu-Cil included, and it comes from the prescription drug data and the manufacturers' own warnings.

Possible effect	How likely and how serious	What to do
Itching, redness, stinging at the lash line	The commonest reaction; usually mild and settles	Pause for a few days, restart every other night; stop if it persists
Darkening of the eyelid skin	Reported in a minority; usually fades on stopping but may not fully reverse	Apply a thin line only to the upper lash base and blot any excess; stop if it appears
Permanent darkening of the iris	Rare with correct application to the skin, but documented with this ingredient class and likely permanent when it occurs; people with mixed-colour eyes are most at risk	Never apply inside the lash line or to the lower lid; this is the reason for the application rules
Hollowing around the eye	Loss of fat around the eye socket is a recognised effect of prostaglandin glaucoma drops and has been reported with lash use of the same drug; uncommon, slowly reversible	Stop if the upper eyelid begins to look deeper or more hollow than before
Hair growth where the product touches	Fine hair can appear on skin the serum repeatedly contacts	Precise application; wipe any stray product
Dry eye, styes, eyelid inflammation	Reported in a small number of users	Stop and seek advice if they develop
Interaction with glaucoma treatment	Can reduce the effect of prostaglandin eye drops on eye pressure	Do not use without speaking to your ophthalmologist

Do not use a prostaglandin-analogue serum if you are pregnant, breastfeeding or trying to conceive; have glaucoma, raised eye pressure or use any prescription eye drops; have had eye surgery, uveitis or macular problems; have an active eye infection, blepharitis flare or eczema on the lids; or are undergoing cancer treatment. If you are prone to dry eyes or styes, check with your GP or optician first. Remove contact lenses before applying and wait fifteen minutes before reinserting.

What the regulators say

You should also know that the regulatory position on these ingredients in cosmetics is unsettled, and moving in one direction.

Authority	Position	What it means for you
EU Scientific Committee on Consumer Safety	In 2022 could not establish the safety of the two main cosmetic analogues; after reviewing new industry data, concluded in 2025 to 2026 that the three analogues assessed are not safe for use in lash and brow growth cosmetics	An EU restriction or ban is possible; the UK is not bound by it but often follows
Health Canada	Banned isopropyl cloprostenate in cosmetics in 2019	One major regulator has already acted
US FDA	Issued a warning letter in 2011 to a lash serum brand over the same ingredient, on the basis that a product with a pharmacological effect is a drug, not a cosmetic	Products are sold with disclaimers that they are "not intended to cause growth" partly for this reason
UK	No specific restriction as of this update; prostaglandin-analogue serums are sold as cosmetics	The product is legal to buy and sell here; the decision to use one is yours, ideally an informed one

Dehydrolatanoprost, the analogue in Nu-Cil, was not among the three the European committee assessed by name. It belongs to the same class with the same pharmacology, and I would treat the committee's reasoning as applying to it until shown otherwise. I will update this article if the UK position changes.

My 12-week results with Nu-Cil

With all of that said, here is what happened when I used the lash and brow serums nightly for twelve weeks, knowing what was in them, with photographs at the start, at six weeks and at twelve. These are one person's results and no more.

Weeks	Lashes	Brows
1 to 2	No visible change. Mascara flaked less. No stinging or redness	Nothing, which is normal at this stage
3 to 4	Curl held better through the day; the outer third looked slightly more fanned	The inner brow looked softer and more even, as if fine new hairs were filling in
6 to 8	Noticeably fuller lash line, especially at the outer corners; one coat of mascara looked polished; less lash loss on make-up removal	Better density through the arch; sparse mid-sections less obvious; less pencil needed
10 to 12	Best result: a denser fringe with a small but definite gain in length, natural rather than extension-like	Tail definition improved; texture smoother and glossier; make-up sat better

I had no irritation, no redness, no darkening of the lid skin and no change to my eye colour. I was careful about application, which I think matters a great deal, and I had none of the risk factors above. The result was exactly what the mechanism predicts: a natural but real increase in density and a modest gain in length, building from about week six.

Would I recommend it? Yes, to the right person: an adult with none of the exclusions above, who understands that this is an active prostaglandin-analogue product rather than a conditioner, who will apply it precisely, and who is prepared to stop if her eyelids darken or her eye area begins to hollow. For someone who wants shinier, better-behaved lashes with no pharmacological activity at all, a conditioning serum is the right choice, and I would say so.

How to use a lash serum safely

Step	How	Why it matters
Clean, dry skin, lenses out	Remove all eye make-up and residue; take contact lenses out first	Oil blocks absorption; lenses can absorb the active
A thin line, upper lash base only	Draw it along the skin where the upper lashes meet the lid, like a very fine eyeliner. One dip serves both eyes	Keeps the active away from the eye surface and the lower lid, which is where the pigment and iris risks come from
Blot any excess	Tissue off anything that strays beyond the lash line	Stray product is what darkens skin and grows hair where you do not want it
Brows: sweep through, then target gaps	Use the dedicated brow applicator, one pass through the brow and a second over sparse areas	Brow hairs grow in several directions and need wider coverage
Nightly, then taper	Once a night until you reach the result you want, usually 12 to 16 weeks, then every other night to maintain	Results reverse over two to three months if you stop; doubling up does not speed anything up
Wait before layering	Give it ninety seconds to dry before eye cream	Stops the active being carried onto skin it should not reach
Photograph and check	Photos at weeks 0, 6 and 12 in the same light; look at lid colour and eye hollowing as well as lashes	The side effects are gradual and easy to miss in the mirror

A lash serum that works is a medicine in a cosmetic bottle. Use it with the respect you would give the medicine, and it is a very good product.

Frequently asked questions

Do eyelash serums actually work?

The ones containing a prostaglandin analogue do, with good evidence for the prescription version and manufacturer evidence for the cosmetic ones. Conditioning-only serums improve the look of lashes but have no evidence of growth.

Does Obagi Nu-Cil contain a prostaglandin?

Yes. Its active "proprietary lipid compound" is dehydrolatanoprost, a prostaglandin analogue related to the glaucoma drug latanoprost. That is why it works and why its packaging carries prostaglandin warnings.

How long before I see results?

Lashes typically show change at six to eight weeks with best results by twelve to sixteen. Brows are slower, eight to twelve weeks or more. The cycle is the limiting factor, and no serum can hurry it.

Will my lashes go back to normal if I stop?

Yes, over two to three months as the hair cycle turns over. Maintenance every other night preserves most of the result.

Can a lash serum change my eye colour?

Permanent darkening of the iris is a documented effect of prostaglandin analogues. It is rare when the product is applied correctly to the skin of the upper lid and never inside the eye or on the lower lid, but it is why those application rules matter.

Can lash serums cause hollow eyes?

Loss of fat around the eye is a recognised effect of prostaglandin glaucoma drops and has been reported with lash use of the same drug. It is uncommon and slowly reversible on stopping. Watch for a deeper upper lid in your progress photographs.

Are prostaglandin lash serums banned?

Not in the UK as of this update. Canada banned one in 2019, and the EU's scientific committee has concluded that the three it assessed are not safe for cosmetic lash use, so an EU restriction is possible. I will update this article if the position changes.

Can I use a lash serum in pregnancy or while breastfeeding?

No. Prostaglandin analogues should be avoided entirely in pregnancy, when breastfeeding and when trying to conceive.

Can I use a lash serum with extensions or a lash lift?

Yes, but pause for 48 to 72 hours after the procedure, avoid saturating the adhesive area, and follow your technician's aftercare.

Is a prescription option available in the UK?

Bimatoprost 0.03% is licensed for lashes in the US and can be prescribed off-licence in the UK by a doctor who has assessed you. It has the strongest evidence and the same side-effect profile. Discuss it with your GP or at a consultation.

Further reading

• We Are Now an Official Obagi Ambassador Clinic
• Is Your Obagi Genuine? How to Buy Obagi Safely in the UK
• Skincare Ingredients I Would Be Careful With
• Hair Loss: Shedding vs Thinning and What Actually Helps
• Under-eye treatment in Hale, for the skin around the lashes
• Medical-grade skincare in Hale, where Nu-Cil fits into a routine

Next steps

Learn more about Dr Caroline Warden Clinic

Click here for price list

Learn more about other treatments offered

About the author

Dr Caroline Warden is an NHS GP with nearly twenty years in medicine, an independent prescriber, and holds a Level 7 postgraduate diploma in cosmetic injectables. She is the sole treating practitioner at Dr Caroline Warden Skin & Aesthetic Clinic, 2 Crown Passages, Hale, Altrincham, Cheshire, an official Obagi Ambassador clinic. GMC number 6157708. The clinic stocks and sells Obagi Nu-Cil; the results described are the author's own, and the clinical study figures quoted for Nu-Cil are the manufacturer's data on file.

References

1. Smith S, Fagien S, Whitcup SM, et al. Eyelash growth in subjects treated with bimatoprost: a multicenter, randomized, double-masked, vehicle-controlled, parallel-group study. Journal of the American Academy of Dermatology. 2012;66(5), pages 801 to 806. Read the abstract.
2. Beer KR, Dunn M, Wilson F. Treatment of eyebrow hypotrichosis using bimatoprost: a randomized, double-blind, vehicle-controlled pilot study. Dermatologic Surgery. 2013. Read the study.
3. Sira M, Verity DH, Malhotra R. Topical bimatoprost 0.03% and iatrogenic eyelid and orbital lipodystrophy. Aesthetic Surgery Journal. 2012. Read the abstract.
4. Scientific Committee on Consumer Safety. Opinion on prostaglandins and prostaglandin-analogues used in cosmetic products, SCCS/1635/21, adopted 3 February 2022. Read the opinion.
5. Scientific Committee on Consumer Safety. Further opinion on prostaglandin analogues in cosmetics (IPCP, DDDE and MDN), 2025 to 2026, summarised by ChemLinked. Read the summary.
6. Obagi Nu-Cil Eyelash Enhancing Serum: full ingredient list, clinical claims and warnings as published by an authorised retailer. Read the listing.
7. Obagi Medical releases new Nu-Cil eyelash serum. Aesthetics Journal. Read the article.