Can latanoprost be safely applied to the scalp, or is it only for eyelashes?

Latanoprost is a drug first designed to treat glaucoma, an eye disease that damages the optic nerve due to increased intraocular pressure. Patients prescribed latanoprost eye drops began to notice an unusual side effect: their eyelashes became longer, darker, and thicker. This observation led to its cosmetic use in eyelash growth. However, a natural question arises: if latanoprost can influence hair growth around the eye, could it also be effective and safe when applied to the scalp?

Latanoprost is classified as a prostaglandin analogue. Prostaglandins are hormone-like substances that regulate many processes in the body, including blood flow, inflammation, and cellular growth. Hair follicles, like miniature organs, go through repeating cycles of growth (anagen), regression (catagen), and rest (telogen). Scientific evidence shows that prostaglandins influence the duration of these cycles. For example, prolonging the anagen phase can result in longer and denser hair. Latanoprost binds to prostaglandin receptors in hair follicles, potentially altering the cycle to favor active growth.

This mechanism became most visible in eyelashes, leading to the FDA approval of bimatoprost (Latisse®) in 2008 for cosmetic eyelash growth. However, the scalp is biologically and structurally different from the eyelid margin. Hair loss on the scalp, particularly androgenetic alopecia, is influenced not only by growth cycles but also by genetic and hormonal factors, especially the action of dihydrotestosterone (DHT). Because of these complexities, the simple transfer of an eyelash treatment to the scalp demands scientific scrutiny.

What the research on scalp application really tells us

The available evidence for latanoprost on the scalp remains limited, and the studies conducted so far are small in scale. Yet they provide important insights into the potential and limitations of this drug.

In 2012, a pilot clinical trial tested latanoprost 0.1% solution in men with early-stage androgenetic alopecia. Sixteen men participated in this randomized, double-blind, placebo-controlled study that lasted 24 weeks. Latanoprost was applied once daily to a defined area of the scalp, and changes were evaluated through macrophotography, a technique that captures highly detailed images of scalp hair density. The results showed a significant increase in hair density compared to placebo. Although promising, the trial’s main weakness was its very small sample size, which makes it difficult to generalize the findings or assess long-term safety. The authors themselves concluded that larger studies were required before considering clinical use. (Blume-Peytavi et al., 2012, Journal of the American Academy of Dermatology).

Earlier in 2002, an animal study explored the effects of topical latanoprost on C57BL/6 mice, a standard model for hair biology. Over several weeks, researchers applied the drug to shaved areas of skin and observed regrowth. The drug accelerated the transition of follicles into the anagen phase, resulting in faster regrowth compared to untreated controls. While this experiment demonstrated a biological mechanism, the criticism lies in the fact that mouse hair cycles differ from human hair cycles. Findings in rodents cannot be directly extrapolated to humans. (Sasaki et al., 2002, Journal of Dermatological Science).

Further evidence comes from a 2012 clinical study on eyebrow hypotrichosis (sparse eyebrow hair). Sixteen patients applied latanoprost daily for four months. Researchers measured hair density and thickness using photographic evaluation and found significant improvement compared to baseline. This trial confirmed that latanoprost can stimulate terminal hair outside eyelashes. However, eyebrows are structurally closer to eyelashes than scalp hair, and the results cannot automatically be transferred to scalp conditions.

Safety concerns when moving beyond eyelashes

Even if latanoprost has shown biological activity on scalp hair follicles, its safety in this context remains unverified. Unlike eyelash application, which involves a very small surface area and a low systemic dose, the scalp presents a much larger area for absorption. This raises several critical concerns.

Scalp irritation is one potential problem. Latanoprost may cause redness, itching, or dryness, which could become more pronounced if applied to larger areas. Skin pigmentation changes are another risk; prostaglandin analogues are known to cause darkening of skin around the eye in some patients. If used widely on the scalp, this effect could result in uneven skin tones. There is also uncertainty about systemic absorption. Although latanoprost is generally safe for ocular use, spreading the drug over the scalp might increase the total absorbed amount, with unknown consequences.

At present, the FDA has only approved prostaglandin analogues such as bimatoprost for eyelashes. Latanoprost use on the scalp is considered off-label, meaning it is not officially approved or guaranteed safe. Therefore, while the available evidence shows biological plausibility, the absence of large-scale human studies makes it impossible to claim safety or long-term efficacy with confidence.

If we ask this question from the perspective of our own search for answers, what do we need to know?

The evidence so far indicates that latanoprost can stimulate hair follicles beyond the eyelashes, including on the scalp. Studies in both humans and animals show increased hair density and faster regrowth under controlled conditions. However, these studies are small, preliminary, and leave important safety questions unanswered. In our current position, we would recognize that latanoprost is not limited to eyelashes, but its use on the scalp remains experimental. The critical point is that larger, longer clinical trials are needed before it could be considered a safe and reliable option.

References

Blume-Peytavi, U., Lönnfors, S., Hillmann, K., & Garcia Bartels, N. (2012). A randomized double-blind placebo-controlled pilot study to assess the efficacy of a 24-week topical treatment with latanoprost 0.1% on hair growth and pigmentation in healthy volunteers with androgenetic alopecia. Journal of the American Academy of Dermatology, 66(5), 794–800. https://pubmed.ncbi.nlm.nih.gov/22264449/

Coronel-Pérez, I. M., Rodrigues-Barata, A. R., & Camacho-Martínez, F. M. (2012). Latanoprost in the treatment of eyebrow hypotrichosis. Journal of the European Academy of Dermatology and Venereology, 26(1), 123–125. https://pubmed.ncbi.nlm.nih.gov/22092886/

Sasaki, S., Hozumi, Y., & Kondo, S. (2002). Influence of prostaglandin F(2α) analogue latanoprost on hair growth in mice. Journal of Dermatological Science, 30(2), 111–118. https://pubmed.ncbi.nlm.nih.gov/12191516/

U.S. Food and Drug Administration. (2008). FDA approves Latisse to treat hypotrichosis of the eyelashes. U.S. Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-approves-latisse-treat-hypotrichosis-eyelashes