Bimatoprost

What it is

Bimatoprost is a synthetic relative of prostaglandin F2-alpha. It was first a glaucoma eye drop (Lumigan), and glaucoma patients noticed their lashes growing. As Latisse (0.03%) it was approved by the US FDA in December 2008 for eyelash hypotrichosis (too few or too short lashes). It is applied along the upper eyelid margin, not dropped into the eye (label).

• US: prescription-only, approved for lashes. Not approved for brows or scalp.
• Japan: marketed for lash hypotrichosis as Glash Vista.
• UK and EU: licensed for glaucoma. Lash use is off-label and by prescription; we found no EU authorisation for a lash indication.

Cosmetic lash serums are a different matter. Some contain bimatoprost or related drugs without declaring it: of 64 serums bought online in Japan, 4 contained bimatoprost (3 not on the label) and 8 contained other prostaglandin analogues (Rahman 2022).

How it works

Bimatoprost prolongs the growth phase of the lash follicle, so more lashes are growing at any moment, and it enlarges the follicle bulb and adds pigment, giving longer, thicker, darker lashes. In mice it lengthened the growth phase but did not create new follicles.

Scalp follicles respond in the lab: bimatoprost increased hair production in cultured human scalp follicles and sped regrowth in mice (one co-author worked for the manufacturer) (Khidhir 2013). A 2026 study of 11 men found 1% to 3% scalp formulations reached at least 10 times the concentration needed for maximal growth in isolated follicles, so poor penetration is probably not why the scalp trials disappointed (Khajeh Pour 2026). In alopecia totalis and universalis it lengthened existing lashes but grew no new ones (Ricar 2022).

What the studies show

Eyelashes (strong evidence)

• In 278 adults over 16 weeks, 78.1% had at least a 1-grade improvement in lash prominence versus 18.4% on vehicle; length, thickness and darkness all improved (Smith 2012).
• Two Japanese trials found responders in 77.3% versus 17.6% (173 people, idiopathic) and 88.9% versus 27.8% (36 people, after chemotherapy) (Harii 2014).
• In 130 people after chemotherapy, responders were 46.9% versus 18.2% at month 6 and 61.5% at month 12 with continued use (Wirta 2015).
• In a 1-year trial, gains held about 2 months after stopping and largely faded by 4 to 6 months; composite responders at month 4 were 40.2% versus 6.8% (Glaser 2015).
• In 71 children and adolescents, 70.8% versus 26.1% improved, but the benefit was significant only in healthy adolescents, not after chemotherapy or in alopecia areata (Borchert 2016).

Eyebrows (fairly good evidence, off-label)

• In 357 adults over 7 months, at least a 1-grade improvement occurred in 83.9% (twice daily), 77.1% (once daily) and 43.0% (vehicle) (Carruthers 2016).
• A 40-person trial of 0.01% found density and hair diameter improved versus vehicle (P<0.001) (Suchonwanit 2019).
• In 60 people, bimatoprost 0.01%, 0.03% and 2% minoxidil gel all improved the brows with no significant difference between them, so minoxidil is a cheaper option (Zaky 2023).

Scalp pattern hair loss (no benefit shown)

• In 307 men over 6 months, three bimatoprost formulations changed hair count by +13.1, +6.1 and +6.3 hairs/cm2 versus +4.1 on vehicle and +21.9 on minoxidil 5% (men's trial).
• In 306 women, bimatoprost changed it by -0.4, -3.5 and +4.3 versus +1.1 on vehicle and +13.6 on minoxidil 2% (women's trial).
• A second men's program (244 men) found +12.7 and +9.3 versus +5.8 on vehicle (trial record).
• These results were posted only on the trial registry, no phase 3 was registered, and the one meta-analysis of prostaglandins for hair loss left them out (Jiang 2023).

Alopecia areata (limited evidence)

• Bimatoprost 0.03% regrew patches faster than mometasone in 30 people over 3 months, with fewer side effects (Zaher 2015), but a small randomised report found no benefit for lashes in alopecia areata (Roseborough 2009).

How it's used in studies

• Lashes: one drop of 0.03% on a sterile single-use applicator, drawn along the upper lid margin at the lash base once nightly. Extra applications do not speed growth (label).
• Trials judged lashes at 16 weeks. The label says lashes return to baseline after stopping.
• Eyebrows: 0.03% once or twice daily for 7 months, or 0.01% once daily for 6 months.
• Scalp (failed programme): about 1 mL of experimental solutions once or twice daily for 6 months.
• Alopecia areata patches: 0.03% twice daily or 0.01% for 12 weeks.

Side effects and safety

• Common: itchy and red eyes and skin darkening, about 3 to 4% each in trials. Less often eye irritation, dry eye and eyelid redness (label).
• Iris darkening: increased brown iris pigment can occur and is likely permanent. Eyelid-skin darkening usually reverses over weeks to months. An independent review argues the iris risk with lid-margin use has never been properly measured (Steinsapir 2021).
• Eyelid fat loss (hollowed upper lids): among four glaucoma prostaglandin drugs compared in 55 patients, bimatoprost caused the most (Li 2025). Blinded graders saw signs of it in companies' own before-and-after photos of prostaglandin lash serums, and one user's hollowing reversed 6 months after stopping (Jamison 2022).
• Hair where you do not want it: solution that repeatedly touches other skin can grow hair there.
• Glaucoma: it may blunt other prostaglandin glaucoma drops, so check with an eye doctor first. Remove soft contact lenses before applying.
• Pregnancy: no adequate studies; the label says to use it only if the benefit justifies the risk.
• Untested or undeclared serums bypass all of these warnings.

Bottom line

For eyelashes, bimatoprost is the best-evidenced option and the only approved one in the US: about three in four users get visibly longer, fuller, darker lashes after roughly four months, and the gains fade after stopping. The costs are a small risk of permanent iris darkening, especially in hazel or brown-green eyes, and eyelid hollowing. For brows it works off-label, and minoxidil gel did as well in one trial. For the scalp it failed to match minoxidil in about 850 people, so do not use it for pattern hair loss. A US retail price list shows roughly $57 to $305 for a Latisse bottle; compounded scalp mixes with minoxidil averaged about $159 per 60 mL in a 2024 survey despite the poor evidence (Choi 2024). Discuss with a doctor.

Fun facts

• Latisse exists because glaucoma patients using prostaglandin eye drops grew noticeably longer lashes; a side effect became the product.
• A year before Latisse was approved, US marshals seized about $2 million of a cosmetic lash product that secretly worked because it contained bimatoprost.