Long4Lashes what’s inside the lash serum.

Long4Lashes is one of the best-known eyelash serums. What’s in it, why it works, what you’re accepting in return – and who we’d point towards an alternative.

ARBUTI Hair Salon · Updated October 2026

Eye with long natural lashes looking upward, close-up

Fact file

Product
Long4Lashes Eyelash Serum (FX5 formula), brush applicator like an eyeliner
Active ingredient
A prostaglandin analogue – bimatoprost according to the ingredients list in the manufacturer’s shop, isopropyl cloprostenate in older retailer listings
How to use
According to the manufacturer, once a day in the evening, on the clean upper lash line
Where to buy
Online and in shops; availability varies from country to country. The manufacturer now also sells a “Day & Night Double Serum” which, according to its ingredients list, contains no prostaglandin analogues.
Who for
Adults with short or weak lashes who know and accept the information on side effects
Not for
Pregnant or breastfeeding women, people with eye conditions, after eye surgery or during glaucoma treatment – check with a doctor first

How Long4Lashes works

Prostaglandin analogues were originally used as eye drops to treat raised pressure inside the eye. Doctors then noticed that patients were growing longer, thicker lashes. Cosmetic lash serums make use of this effect: they extend the growth phase of the lashes. That’s why serums containing these substances are considered the more effective ones – and also why they are viewed critically.

In its final opinion in February 2026, the EU’s Scientific Committee on Consumer Safety (SCCS) classified several prostaglandin analogues in lash and brow serums as unsafe, including isopropyl cloprostenate. As of October 2026, no legal restriction has yet been adopted. The French agency ANSES warns of possible changes in eye colour.

Possible side effects

  • Redness, burning or itching on the eyelid and eye
  • Darkening of the eyelid skin
  • In rare cases, a change in iris colour, especially in light or mixed-colour eyes
  • Hair growth wherever serum gets onto the skin

If you experience any discomfort, stop using the serum, and if symptoms persist, see an eye doctor. If you use eye drops for glaucoma, only use prostaglandin serums after talking to your doctor.

Long4Lashes and our alternative

1Lazru Eyelash and Eyebrow Serum

Our pick, no prostaglandin

Lazru Eyelash and Eyebrow Serum

A serum for lashes and brows without prostaglandins and without hormones – according to the published ingredients list, with the actives Procapil™ and AnaGain™ plus caffeine. Dermatest rated its skin tolerance “very good” (06/2022). The manufacturer cites first changes after a few weeks and more noticeable ones after two to four months – it varies from person to person.

What we like

  • No prostaglandin analogues and no hormones
  • For lashes and brows
  • Dermatest “very good” (skin tolerance)

Keep in mind

  • Needs patience: use for at least two months
  • Pricier than drugstore serums
See the comparison
2Long4Lashes Eyelash Serum

Strong, with prostaglandin

Long4Lashes Eyelash Serum

A well-known serum containing a prostaglandin analogue. This class of active ingredient has been shown to stimulate lash growth. In return, you should know the possible side effects and apply the serum carefully, only along the lash line.

What we like

  • Active class with a proven effect on lash growth
  • Precise brush
  • Easy to apply

Keep in mind

  • Contains a prostaglandin analogue
  • Possible eyelid discolouration and eye irritation
  • Not during pregnancy or breastfeeding
View on Amazon

You’ll find an overview of all eyelash serums – with and without prostaglandins – in our eyelash serum top list. RevitaLash also works with a prostaglandin-type active ingredient.

Frequently asked questions

Does Long4Lashes contain hormones?

Not in the sense of sex hormones. But it does contain a prostaglandin analogue – a derivative of prostaglandins, which are hormone-like messenger substances in tissue. That’s why people often talk about “hormones”.

Does Long4Lashes work?

Prostaglandin analogues are among the actives with the most noticeable effect on lash growth. How strong and how quick the effect is varies from person to person.

What are the side effects of Long4Lashes?

Possible effects include irritated, red eyes, darker eyelid skin and, rarely, a change in eye colour. If you experience any discomfort, stop using it and get it checked by a doctor.

Is there a prostaglandin-free alternative?

Yes. Our recommendation is Lazru, a serum for lashes and brows without prostaglandins and without hormones. More on this in our eyelash serum comparison.

Can I use Long4Lashes during pregnancy?

No, we advise against it. Talk to your doctor or midwife.

Read next

Lashes & Brows
Lazru serum for lashes and brows, 3.5 ml tube with brush applicatorGuide · Lashes & BrowsLazru Serum review: what it can do for lashes and brows.One serum for lashes and brows – no prostaglandins, no hormones. What’s inside, how to use it, what’s proven and what isn’t – and why it takes first place in our comparison.Woman placing a strip of false lashes while looking into a hand mirrorGuide · Lashes & BrowsMagnetic lashes: false lashes without the glue.Magnetic lashes stay put with tiny magnets instead of glue. How the two systems work, what to watch out for if you have sensitive eyes – and when another option suits you better.Fine brush tracing the upper lash line on a closed eyeTest · Lashes & BrowsEyelash serum: with or without prostaglandins?Eyelash serums differ above all in one respect: whether or not they contain a prostaglandin analogue. That determines how well they work, the possible side effects – and which serum is right for you.