Does lash serum work? What's really in lash growth serums

Lash serum searches keep climbing in the US, led by brand names like Sweed, Hanae, Dr. Althea and The Ordinary's Multi-Peptide Lash and Brow Serum. Behind most of them is one question: does lash serum work?

It depends on what's in the tube. Lash serums fall into two very different groups. Only one has strong evidence for growing lashes, and that same group carries the side effects people worry about.

Prostaglandin lash serums contain an ingredient related to bimatoprost, the drug in prescription Latisse. On a label it can appear as isopropyl cloprostenate, dechloro dihydroxy difluoro ethylcloprostenolamide (also sold as ethyl tafluprostamide), methylamido-dihydro-noralfaprostal or norbimatoprost. GrandeLASH-MD is a well-known example: its ingredient list includes isopropyl cloprostenate, and the brand calls it a prostaglandin analog.

Conditioning lash serums skip the prostaglandin and use peptides, panthenol, amino acids and plant extracts. The Ordinary's Multi-Peptide Lash and Brow Serum ($14.90) is one of these. Its main actives are four peptides (myristoyl pentapeptide-17, biotinoyl tripeptide-1, oligopeptide-2 and acetyl tetrapeptide-3), plus caffeine and panthenol.

A French review of 79 lash products published this year found that about 30% contained a prostaglandin analogue. The rest relied on ingredients such as castor oil, amino acids, panthenol and peptides.

Latisse (bimatoprost 0.03%) has been FDA-approved since 2008 for thin or sparse lashes. In its main trial, 278 adults applied either bimatoprost or a plain solution along the upper lash line every night. At 16 weeks, 78% of the bimatoprost group had visibly fuller lashes on the doctor's rating scale, compared with 18% on the plain solution, and image analysis showed gains in length, thickness and darkness.

According to the label, the difference showed up by week 8. Extra drops don't speed things up, and lashes drift back to how they were once you stop.

Cosmetic prostaglandin serums use chemical cousins of bimatoprost, added for the same lash-boosting effect. They haven't been through drug trials like the one above, and they come without the dosing rules and warnings of a prescription.

Most of what's known comes from bimatoprost studies. Expect the cosmetic cousins to carry the same kinds of risk.

• Red, itchy eyes and itchy lids. These were the most common problems in six trials covering 680 people on bimatoprost, and they were usually mild and went away after stopping.
• Darker eyelid skin. The Latisse label says this usually fades once you stop.
• Eye color change. The label warns that brown pigment in the iris can increase and is likely to be permanent. A chart review of 50 long-term cosmetic users found no iris changes, but a UCLA review concluded this risk still hasn't been studied well enough.
• Hollowing around the eyes. Prostaglandin glaucoma drops are known to shrink the fat around the eye. A 2022 study found signs of this in brands' own before-and-after photos for prostaglandin lash serums, and described a woman whose eyes looked hollow after 10 months of a serum with isopropyl cloprostenate. It reversed six months after she stopped.
• Hair where you don't want it. Serum that runs onto the cheek can grow hair there, so blot any excess.
• If you use glaucoma eye drops, talk to your eye doctor first. An extra prostaglandin can make those drops work less well.

In the US, a product sold to grow lashes that contains a drug ingredient can be treated as an unapproved drug. In 2007, at the FDA's request, US marshals seized 12,682 tubes of a lash conditioner called Age Intervention Eyelash because it contained bimatoprost.

In February 2026, the EU's Scientific Committee on Consumer Safety concluded that none of the three prostaglandin analogues it reviewed, isopropyl cloprostenate included, can be considered safe in lash and brow cosmetics, even at the low strengths the industry proposed. Its main concern was missing data on harm during pregnancy, since users are most likely to be women of child-bearing age.

Labels don't always tell you, either. When Japanese researchers tested 64 lash serums bought online, four contained bimatoprost and three of those didn't list it. Eight more contained other prostaglandin analogues.

There's much less to go on. The best published study we found tested one peptide and glycosaminoglycan serum on 30 women for 12 weeks. Lashes measured about 8% longer and 10% thicker by the end. There was no comparison group, and the study was run by the company that makes the serum.

Peptides and panthenol can condition lashes, which may help if yours snap from curling, mascara removal or extensions. Just don't expect the visible change a prostaglandin gives.

Castor oil is the classic DIY pick. We couldn't find a controlled trial showing it grows lashes.

• Read the ingredient list for the prostaglandin names above. If one is there, you're buying the stronger kind with the side effects.
• If you want real growth, ask a doctor about prescription bimatoprost. You get a tested dose and someone to check your eyes.
• Pregnant, breastfeeding, trying to conceive or using glaucoma drops? Choose a peptide serum or skip lash serum altogether.
• Apply a thin line along the upper lash line only, on clean skin with contact lenses out, and blot anything that spreads.
• Give it 8 to 16 weeks. Whatever you gain fades after you stop.
• Stop if your eyes stay red or sore, your lids darken, or the area around your eyes starts to look hollow.

Lashes grow in cycles, and only some are growing at any one time. Bimatoprost is thought to push more lashes into the growth phase and keep them there longer, so they end up longer, thicker and darker. Doctors first noticed the effect in glaucoma patients using prostaglandin eye drops.

The same drug family acts on pigment cells and fat cells around the eye, which explains the darker lids, the iris risk and the hollowing. Peptide lash serums work on the surface of the lash and have no comparable drug effect, which is why they're gentler and why the results are smaller.

• Prescription bimatoprost 0.03% (Latisse) for longer, thicker, darker lashes.well-supported
• Cosmetic lash serums with prostaglandin analogues such as isopropyl cloprostenate.limited evidence
• Peptide and panthenol lash serums for length and fullness.limited evidence

• Castor oil growing lashes.
• The safety of cosmetic prostaglandin analogues in pregnancy; the EU safety committee says the data aren't there.
• Long-term iris and eye-area safety of cosmetic prostaglandin serums.