Latanoprost

What it is

Latanoprost is a prodrug of prostaglandin F2-alpha and was the first drug of its type launched for glaucoma and raised eye pressure. The standard product is a 0.005% eye drop, prescription-only. No regulator we found has approved it for lashes, brows or scalp hair, so every hair use is off-label. The prostaglandin analogue that is approved for lashes in the US is bimatoprost.

How it works

Latanoprost acid activates the prostaglandin F receptor, which is found in the dermal papilla, the follicle's control centre. In lashes it appears to push resting follicles into growth and prolong that growth, which explains the extra number, length and thickness. It also stimulates pigment production, which is why lashes and irises darken.

Balding scalp has less PGF2-alpha and more PGD2 than haired scalp, which is one rationale for scalp use (see prostaglandins and hair). In a 2025 lab study, natural PGF2-alpha lengthened hair fibres from human facial-skin follicles, with a bigger effect in miniaturised "intermediate" follicles (+10.0%) than terminal ones (+4.9%); a receptor blocker abolished it. This is lab data only (Miranda 2025).

What the studies show

Eyelashes (fairly good evidence, from glaucoma use)

• Glaucoma patients treated in one eye grew more, longer, thicker, curlier and darker lashes on that side only (Johnstone 1997, 43 patients).
• In 17 patients, lash length rose from 5.8 to 6.6 mm by week 10 (P<0.001) while the untreated eye did not change (Sugimoto 2002).
• There is no cosmetic RCT of latanoprost for lashes; bimatoprost has those.

Scalp pattern hair loss (limited evidence)

• In stump-tailed macaques with scalp baldness, 0.005% caused minimal growth and 0.05% caused moderate-to-marked regrowth (Uno 2002, 8 animals).
• In a 16-man double-blind pilot, 0.1% for 24 weeks raised hair density versus baseline (P<0.001) and versus a placebo scalp zone (P=0.0004) (Blume-Peytavi 2012).
• In 29 women, latanoprost acid at 0.01%, 0.05% and 0.1% gained +17.8, +23.5 and +16.5 hairs/cm2 within each arm over 6 months, with no difference between doses and only two women on vehicle; the authors hold a patent (Rakowska 2026).
• A company study of a combination of minoxidil, finasteride and latanoprost (TH07) rated it better than any single ingredient, with no placebo arm and authors employed by the developer (Sekhavat 2023). A 420-man phase 3 began in April 2026 with primary completion expected December 2027 (trial record).
• A meta-analysis of six small RCTs found a large pooled benefit but high heterogeneity, mixed in a non-prostaglandin drug (cetirizine), and left out the large negative bimatoprost scalp trials (Jiang 2023).

Alopecia areata (limited and conflicting evidence)

• No effect on brows and lashes: 1 of 26 had partial regrowth on the treated side (Faghihi 2009); a short randomised report also found no benefit (Roseborough 2009).
• In 54 people with alopecia universalis followed for 2 years, 45% of treated versus 0% of controls had cosmetically acceptable lash regrowth (Coronel-Pérez 2010).
• In 100 people with patchy disease, latanoprost, minoxidil 5% and betamethasone all beat vehicle (El-Ashmawy 2018). Against betamethasone in 50 people, complete response was 24% versus 56% (P=0.02) (Bhat 2021). Added to clobetasol in 30 people, it improved density and regrowth scores but not patch area or SALT score (Rafati 2022).

How it's used in studies

• Glaucoma and lash data: 0.005% eye drops, one drop nightly.
• Lashes in alopecia areata: one drop of 0.005% spread on the lid margins nightly for up to 2 years.
• Scalp: 0.1% once daily for 24 weeks, or latanoprost acid 0.01% to 0.1% once daily for 6 months.
• Lashes lengthened measurably within 2 weeks; scalp studies ran 6 months.
• Compounded scalp mixes in the US: a 2024 survey of 79 pharmacies found a mean price of $141.91 per 60 mL for minoxidil 5% with latanoprost 0.02% (Choi 2024).

Side effects and safety

• Iris darkening (permanent). Common with glaucoma use, mostly in mixed-colour irises, usually starting within 8 months, and not reversing after stopping. One-year incidence was 12% (US), 23% (UK) and 11% (Scandinavia), highest in green-brown eyes (Wistrand 1997). In a 5-year study, 74% of colour changes began within 8 months and none after month 36 (Alm 2004). Treating one eye can leave permanently different-coloured eyes.
• Lash and eyelid-skin darkening fades after stopping; iris changes do not.
• Sunken upper lids (periorbitopathy): 13.6% of 22 long-term users had a deepened upper-lid sulcus (Nakakura 2015). Of four prostaglandin drugs in 55 patients, latanoprost caused the least and bimatoprost the most (Li 2025).
• Red eyes are common, though less than with other prostaglandin drugs. Hair growth around the eye is very common.
• On the scalp, the trials reported no serious problems, but they were tiny; one case report describes a crusting scalp disorder after use.
• Systemic effects are essentially absent at eye-drop doses.
• Pregnancy and breastfeeding: the UK product information says not to use it in pregnancy and advises against use while breastfeeding.
• Anyone already on glaucoma drops should not add a second prostaglandin without their eye doctor.

Bottom line

Latanoprost clearly lengthens and darkens lashes in people who use it as eye drops, but for cosmetic lashes the trial-tested, approved product is bimatoprost. Its main cost is the risk of permanent iris darkening, highest in hazel and green-brown eyes. For the scalp it is a promising idea backed by one 16-man pilot and monkeys, never an adequately powered placebo-controlled trial, so do not choose it over minoxidil; it mainly appears as one ingredient in compounded mixes. In alopecia areata it is weaker than a strong steroid and at most a possible add-on. Discuss with a doctor.

Fun facts

• Its hair-growing power was spotted because glaucoma patients treated in only one eye grew visibly longer, thicker, darker lashes on that side only (Johnstone 1997).