Melatonin (topical)

What it is

Melatonin is the hormone of the pineal gland that regulates sleep and seasonal rhythms. Many mammals use it to time seasonal coat changes (Fischer 2008). Human scalp follicles make their own melatonin, at levels far above blood levels, and carry melatonin receptors (Kobayashi 2005).

This page covers topical use only. In Europe, topical melatonin hair solutions are sold as cosmetics; the best-studied one contains 0.0033% melatonin plus ginkgo and biotin. Oral melatonin is regulated differently (a supplement in the US, prescription-only in the UK). In the US, a regrowth claim would make a topical product an unapproved drug.

How it works

• Follicles synthesize melatonin in the outer root sheath. Mouse skin expresses the MT2 receptor in a hair-cycle-dependent pattern, peaking in catagen (Kobayashi 2005).
• Proposed roles are anti-apoptotic (delaying catagen), antioxidant and DNA-protective (Fischer 2008).
• In 3D human dermal papilla spheroids, melatonin increased hair-inductive genes and beta-catenin activity (Bae 2022). In mice, melatonin promoted regrowth after depilation, and a receptor blocker suppressed it (Niu 2024).

What the studies show

• In 40 women with androgenetic or diffuse alopecia, a 0.1% solution once daily for 6 months raised the occipital anagen rate versus placebo in androgenetic alopecia (n=12, P=0.012) and the frontal anagen rate in diffuse alopecia (n=28, P=0.046). Other comparisons were not significant. Fischer 2004
• Topical 0.01-0.03% melatonin raised blood melatonin to 9-19 pg/mL in 15 volunteers, within the physiological range. Fischer 2004 penetration
• Five studies of a 0.0033% solution reported hair density rising from 123 to 173 hairs/cm² in 35 men over 6 months and positive hair-pull tests falling from 61.6% to 7.8% in 1,891 people. None had a control group for hair outcomes, all were performed for the product's developer, and the solution also contained ginkgo and biotin. Fischer 2012
• Melatonin in vitamin C nanovesicles gave more thickness and density and less hair loss than plain melatonin solution in people with androgenetic alopecia. Hatem 2018
• A review of 11 human studies (2,267 patients) found 8 positive for topical melatonin in androgenetic alopecia. Babadjouni 2023
• Another review concluded that most hair studies fail to show clear efficacy because of weak designs or added actives, and that only the 2004 trial suggests a benefit, in some forms of alopecia in women. Greco 2024

No independent placebo-controlled trial has been published since 2004.

How it's used in studies

• 0.1% melatonin in an alcoholic solution on the scalp once daily for 6 months (Fischer 2004).
• 0.0033% melatonin (with ginkgo and biotin) once daily in the evening for 90-180 days (Fischer 2012).

Side effects and safety

• The large uncontrolled study rated tolerability good in most assessments, with occasional itching, redness or burning (Fischer 2012).
• Some is absorbed, but blood levels stayed within the normal physiological range, below the night-time peak (Fischer 2004). Evening application matches the body's own rhythm.
• It is a hormone with some systemic absorption, and there are no pregnancy data for topical use. People who are pregnant or breastfeeding should avoid it or ask a doctor first.

Bottom line

Topical melatonin is a gentle, non-drug leave-on option for women and men with early androgenetic thinning or diffuse shedding who accept weak evidence. It is not a substitute for minoxidil. See cosmetic hair growth serums. Discuss with a doctor.

Limited evidence: the biology is genuinely interesting, and there is one small positive placebo-controlled trial in women measuring anagen rate rather than visible density. Everything else is uncontrolled and sponsored by the manufacturer.

Fun facts

• Your hair follicles make their own melatonin, at concentrations far above those in your blood (Kobayashi 2005).
• Animals use melatonin to time seasonal coat moults, which is why cashmere-goat farmers study it (Fischer 2008).