Longer, darker lashes are having a moment. For those avoiding the risk or expense of lash extensions , serums can seem like a safer, more affordable option. But not all lash serums are created equal - and some come with hidden side-effects.
Authors
- Alison Ng
Lecturer in Optometry and Vision Sciences, Cardiff University
- Byki Huntjens
Honorary senior research fellow in Optometry, School of Health & Medical Sciences, City St George's, University of London
The key difference lies in the ingredients. Some lash serums use conditioning agents like peptides or plant oils, while others contain powerful pharmaceutical ingredients originally developed for treating eye disease.
In 2001, a new medication called bimatoprost was approved to treat glaucoma and ocular hypertension - two conditions involving pressure buildup inside the eye that can damage the optic nerve and cause vision loss.
Unlike earlier treatments, bimatoprost worked well for patients who hadn't responded to other drugs, had fewer systemic side effects (effects on the whole body rather than just the eye) and required less frequent dosing than some other glaucoma drops .
But doctors soon noticed something unexpected: their patients' eyelashes were growing longer, thicker and darker.
Researchers still don't fully understand how bimatoprost stimulates lash growth, but it appears to extend the anagen phase - the active growth phase - of the lash life cycle .
In 2008, the same drug (now marketed as Latisse) was approved by the US Food and Drug Administration (FDA), the federal agency responsible for evaluating the safety and effectiveness of drugs and medical devices, to treat eyelash hypotrichosis, a condition where eyelashes are sparse or missing.
It was initially prescribed for people who had lost their lashes due to chemotherapy, alopecia areata (an autoimmune disorder causing hair loss), or trichotillomania (a compulsive hair-pulling condition).
Extensive research shows that bimatoprost is effective at making lashes longer, thicker and darker , with noticeable results after 16 weeks of daily use. But the results are temporary: once you stop using it, your lashes return to their natural growth cycle.
Side-effects
Bimatoprost belongs to a class of medications called prostaglandin analogues (PGAs), which have been widely used in eye care since the 1990s. Because of this, its side-effects are well documented. When used for lash growth, bimatoprost can cause burning , redness, dryness and eye irritation . These usually go away when the product is stopped.
But there are also more serious cosmetic changes to be aware of, including darkening of the skin on the eyelid, fat loss around the eyes, creating a hollow, sunken look, permanent iris darkening (the coloured part of the eye), unwanted hair growth where the serum spreads and, in rare cases, drooping of the upper eyelid , which may require surgery to correct.
In the UK, bimatoprost remains a prescription-only medication. However, the boom in over-the-counter lash serums sold online and in shops has made similar products more accessible - and potentially more confusing.
A recent investigation by the UK government found that almost one in four lash serums sold in the UK contain PGAs such as isopropyl cloprostenate. This chemical is not as well studied as bimatoprost, but case reports suggest it can cause skin darkening , dryness and hollowing of the eye area , sometimes after just a few weeks of use.
In the US, the FDA issued warnings over a decade ago stating that any cosmetic product containing these ingredients and making growth claims should be treated as a drug, not a cosmetic.
Consumers may be unaware they're using a pharmaceutical-mimicking ingredient. Sweden banned PGAs in lash serums in 2013. Canada prohibits them in all cosmetic products. Even if a product claims to be "PGA-free," check the ingredients list: anything ending in "-prost" is a red flag.
'Natural' or peptide-based alternatives
Some lash serums use peptides, which may help strengthen lashes by boosting keratin or supporting follicle health. These are often combined with conditioning agents to reduce breakage. While seen as a gentler alternative to PGAs, most studies on peptides focus on scalp hair, not eyelashes , so evidence for lash growth is limited.
Other serums rely on castor oil or plant-based extracts, but their effectiveness is largely anecdotal and not supported by robust science .
There is no guaranteed, side-effect-free way to make lashes grow dramatically longer. Prescription lash serums like bimatoprost are proven to work - but they come with potential risks, especially with long-term use. Over-the-counter products may seem safer, but many contain hidden prostaglandin analogues buried deep in the ingredients list with similar side effects. Peptide and oil-based serums are less risky, but there's little strong evidence that they work.
Our eyes are delicate and, unlike beauty trends, they're not replaceable. If you're thinking about enhancing your lashes, read the label, do your research and speak to an eye care professional. The price of longer lashes shouldn't be your eye health.
Alison Ng is affiliated with the British Contact Lens Association (BCLA), a charitable membership organisation, which disseminates evidence-based practice guidance for eye care practitioners. Alison Ng is a member of the Association of Optometrists (AOP), whose role is to protect, support and represent eye care practitioners in the UK in protecting the nation's eye health.
Byki Huntjens is President of the British Contact Lens Association (BCLA), a charitable membership organisation, which disseminates evidence-based practice guidance for eye care practitioners. Byki Huntjens is an employee the Association of Optometrists (AOP), whose role is to protect, support and represent eye care practitioners in the UK in protecting the nation's eye health.
