Topic
Prostaglandins and hair
Prostaglandins are fat-derived signals that switch follicles on or off; eye drops that copy one of them grow eyelashes but have not worked on the scalp.
Key takeaways
- Eyelashes: proven. Bimatoprost 0.03% (Latisse) is FDA-approved for lash hypotrichosis; in a 278-person trial 78.1% had at least a 1-grade improvement in lash prominence versus 18.4% on vehicle at 16 weeks (Smith 2012). See bimatoprost.
- Eyebrows: good evidence, off-label. A 357-person industry trial found 77.1 to 83.9% improved versus 43.0% on vehicle (Carruthers 2016).
- Scalp: not proven, and bimatoprost failed. In a 307-man company trial, bimatoprost formulations changed hair count by +6.1 to +13.1 hairs/cm2 versus +4.1 on vehicle and +21.9 on minoxidil 5% (trial record). Latanoprost has one 16-man pilot that was positive (Blume-Peytavi 2012) and no adequate trial; a phase 3 of a triple combination containing it is running (TH07).
- The PGD2 side has failed in people: an oral blocker of the PGD2 receptor GPR44 (setipiprant) did nothing in 169 men (trial record), and topical cetirizine has only small, mixed trials.
- Gains fade when you stop: lash benefit largely disappeared 4 to 6 months after stopping in a 1-year trial (Glaser 2015).
- Risks: eye redness and itching, and for products near the eye, permanent iris darkening and eyelid fat loss. Many unregulated "lash serums" secretly contain prostaglandin analogues.
The science
- Balding scalp has more PGD2 than haired scalp, and PGD2 inhibited hair growth in cultured human follicles and mice through the GPR44 receptor (Garza 2012).
- PGF2-alpha analogues (latanoprost, bimatoprost, travoprost) act on the FP receptor in the dermal papilla, prolong the growth phase and enlarge the bulb. In lashes they also darken the shaft.
- Natural PGF2-alpha lengthened hair fibres from human facial follicles in the dish, with a larger effect on miniaturised "intermediate" follicles than terminal ones; this is lab data only (Miranda 2025).
- Drug delivery is probably not the obstacle on the scalp: a 2026 study found scalp drug levels well above those needed in isolated follicles (Khajeh Pour 2026). The scalp failure is probably biological, with androgen-driven miniaturisation overpowering growth-phase prolongation, but that is an inference.
Comparison
| Compound | Use | Status (10 Oct 2026) | Notes |
|---|---|---|---|
| Bimatoprost 0.03% | Lashes | US-approved (Latisse, 2008); prescription-only; UK and EU use off-label | Best studied; industry-funded |
| Latanoprost 0.005% | Lashes, brows, scalp (off-label) | Prescription glaucoma drug | Cheaper; fewer trials |
| Setipiprant | Scalp | Never approved | Failed phase 2 |
| Cetirizine 1% | Scalp | Compounded | Small RCTs |
What it means by hair profile
- Relevant mainly to anyone wanting lash and brow density, including after chemotherapy, and to people exploring add-ons for scalp thinning. Curl pattern and strand thickness are not studied.
- People with light green or hazel irises should know the iris-darkening risk applies to products that reach the eye.
Myths and facts
- Myth: cosmetic lash serums are the same as Latisse. Fact: regulated cosmetic serums differ, and some unregulated ones contain undeclared bimatoprost; 4 of 64 serums bought in Japan did (Rahman 2022).
- Myth: it will grow lashes where none remain. Fact: it lengthens existing lashes; no new lashes appeared in alopecia totalis or universalis (Ricar 2022).
- Myth: eye drops on the scalp are a minoxidil alternative. Fact: bimatoprost lost to minoxidil in the company trials, and latanoprost is untested at scale.
Practical recommendations
- For lashes and brows: use a prescription product with a clinician, understand it must be continued, and avoid unlabelled serums.
- For the scalp: prioritise minoxidil and, for men, finasteride; treat prostaglandin mixes as an experiment.
Bottom line
Prostaglandin analogues are a proven lash treatment and a reasonable off-label brow treatment, but not a scalp treatment. Discuss with a doctor.
Studies 12
Garza LA et al. Prostaglandin D2 inhibits hair growth and is elevated in bald scalp of men with androgenetic alopecia. Sci Transl Med. 2012
Tested: PGD2 measurement and exposure
Result: PGD2 was higher in bald scalp and inhibited hair growth in cultured follicles and mice through the GPR44 receptor.
Read the study ↗Smith S et al. Eyelash growth in subjects treated with bimatoprost: a multicenter, randomized, double-masked, vehicle-controlled, parallel-group study. J Am Acad Dermatol. 2012
Tested: bimatoprost 0.03% vs vehicle on the upper lash line
Result: At least a 1-grade improvement in lash prominence in 78.1% vs 18.4% on vehicle; length, thickness and darkness all improved.
Read the study ↗Carruthers J et al. Bimatoprost 0.03% for the treatment of eyebrow hypotrichosis. Dermatol Surg. 2016
Tested: bimatoprost 0.03% twice daily or once daily vs vehicle
Result: At least a 1-grade improvement in 83.9% (twice daily), 77.1% (once daily) and 43.0% (vehicle).
Read the study ↗Allergan. Safety and efficacy study of bimatoprost in the treatment of men with androgenic alopecia. ClinicalTrials.gov NCT01325337. Results posted 2014
Tested: three bimatoprost formulations vs vehicle vs minoxidil 5%
Result: Hair-count change was +13.1, +6.1 and +6.3 for bimatoprost vs +4.1 for vehicle and +21.9 hairs/cm2 for minoxidil.
Read the study ↗Blume-Peytavi U et al. A randomized double-blind placebo-controlled pilot study to assess the efficacy of a 24-week topical treatment by latanoprost 0.1% on hair growth and pigmentation in healthy volunteers with androgenetic alopecia. J Am Acad Dermatol. 2012
Tested: latanoprost 0.1% vs placebo on two scalp zones per man
Result: Hair density rose versus baseline (P<0.001) and versus the placebo zone (P=0.0004).
Read the study ↗Glaser DA et al. Long-term safety and efficacy of bimatoprost solution 0.03% application to the eyelid margin for the treatment of idiopathic and chemotherapy-induced eyelash hypotrichosis: a randomized controlled trial. Br J Dermatol. 2015
Tested: bimatoprost 0.03% vs vehicle, with a stop-treatment period
Result: Composite responders at month 4 were 40.2% vs 6.8% (idiopathic); gains held about 2 months after stopping and largely faded by 4 to 6 months.
Read the study ↗Show 6 more studies
ClinicalTrials.gov NCT02781311. A safety and efficacy study of setipiprant tablets in androgenetic alopecia in males. Allergan
Tested: setipiprant 1000 mg twice daily vs placebo
Result: Target-area hair count changed by 7.1 vs 6.7 on placebo (difference 0.4, P=0.92); self-assessment was also no different.
Read the study ↗ClinicalTrials.gov NCT07435012. Phase III trial of TH07 topical treatment in men with androgenic alopecia. Triple Hair Inc
Tested: topical minoxidil, finasteride and latanoprost combination
Result: Registered phase 3 trial that began in April 2026 with primary completion expected December 2027; no results yet.
Read the study ↗Miranda BH et al. Prostaglandin F2-alpha stimulates the growth of human intermediate hair follicles in ex vivo organ culture. Front Physiol. 2025
Tested: PGF2-alpha 100 nM
Result: Fibres grew longer, by 10.0% in miniaturised intermediate follicles vs 4.9% in terminal follicles; an FP-receptor blocker abolished the effect.
Read the study ↗Khajeh Pour S et al. Local pharmacokinetics and tolerability of topically-applied bimatoprost to the scalp of male patients with androgenetic alopecia. Clin Transl Sci. 2026
Tested: 1% to 3% bimatoprost scalp formulations
Result: Scalp levels reached at least 10 times the concentration needed for maximal growth in isolated follicles.
Read the study ↗Rahman MS et al. Screening and quantification of undeclared PGF2-alpha analogs in eyelash-enhancing cosmetic serums using LC-MS/MS. J Pharm Biomed Anal. 2022
Tested: laboratory analysis
Result: 4 of 64 serums contained bimatoprost (3 not declared on the label) and 8 contained other prostaglandin analogues.
Read the study ↗Ricar J et al. Topical bimatoprost in the treatment of eyelash loss in alopecia totalis and universalis: a prospective, open-label study. Dermatol Ther. 2022
Tested: topical bimatoprost on the lashes
Result: Only existing lashes grew; no new lashes appeared.
Read the study ↗Related
- BimatoprostA prostaglandin-like eye medicine that grows longer, thicker, darker eyelashes (and helps eyebrows), but did not work on the scalp.
- LatanoprostA cheap glaucoma eye drop that lengthens and darkens eyelashes, with only a small pilot trial behind its off-label use on the scalp.
- SetipiprantAn oral blocker of the PGD2 receptor GPR44 that was tested for male pattern baldness on strong lab data and grew no more hair than placebo in 169 men.
- Topical cetirizineThe common allergy antihistamine, made up as a 1% scalp solution, has several small trials suggesting a modest effect that is weaker than minoxidil.
- MinoxidilThe most widely used hair-growth treatment, available as a cheap over-the-counter lotion or foam and as a prescription tablet, with a mechanism that is still only partly understood.