Melatonin is a hormone widely recognized for regulating the body’s internal clock and is commonly available as a supplement to support sleep. Its production naturally rises in the evening, signaling the onset of rest and establishing the sleep-wake cycle. Recent scientific exploration, however, suggests this molecule may also influence hair health and growth.
Melatonin’s Primary Biological Function
Melatonin is primarily a neurohormone produced in the pineal gland, located deep within the brain. Its main function is to synchronize the body’s physiological processes with the 24-hour light-dark cycle, known as the circadian rhythm. The pineal gland releases melatonin into the bloodstream when light exposure decreases, typically a few hours before bedtime. This surge communicates the time of day to the rest of the body, preparing it for sleep.
Melatonin acts as an endogenous synchronizer, reinforcing various biological rhythms beyond the sleep-wake cycle. It is a chemical signal that increases the propensity for sleep by regulating the timing of the sleep phase, rather than a sedative. This traditional role is the foundation of its popular use as a dietary supplement for managing jet lag and certain sleep disorders.
The Scientific Connection to Hair Follicles
The connection between melatonin and hair growth stems from the discovery that hair follicles themselves are sites of extrapineal melatonin synthesis. This means the scalp’s tissues can produce the hormone, suggesting a localized regulatory function distinct from sleep regulation. Melatonin acts as a local signaling molecule within the hair follicle, interacting with specific membrane receptors, including MT1 and MT2, allowing the follicle structure to respond directly to the hormone.
A primary proposed mechanism involves melatonin’s powerful antioxidant properties, which counteract oxidative stress in the hair follicle. Oxidative damage, often caused by environmental factors or aging, can prematurely push hair follicles out of the active growth phase. By acting as a scavenger of reactive oxygen species, melatonin protects follicular cells and stabilizes the hair growth cycle, which consists of three main phases: anagen (growth), catagen (transition), and telogen (rest).
Melatonin appears to influence the hair cycle by prolonging the anagen phase, the period of active hair production. Keeping the hair in this growth phase supports increased hair density and length. The hormone also modulates gene expression pathways, such as the WNT signaling pathway, which supports the proliferation of dermal papilla cells that govern hair growth.
Practical Application and Usage for Hair Growth
For promoting hair growth, melatonin is typically formulated for topical application directly onto the scalp rather than oral ingestion. This method is preferred because it delivers a high local concentration to the hair follicles. The goal is to maximize the localized effect without significantly increasing bloodstream concentration, which could affect the natural sleep rhythm. Studies show topical application results in minimal systemic absorption, keeping serum melatonin levels within a normal physiological range.
Melatonin products are available as solutions or serums, with effective concentrations ranging from 0.0033% to 0.1%. Application is usually recommended once daily, often in the evening, to align with the hormone’s natural circadian rhythm. Consistency is necessary, with studies suggesting a treatment period of at least 90 to 180 days to observe measurable changes in hair density or shedding.
Serious side effects are rare, but some individuals report mild, transient adverse reactions at the application site. These minor issues include temporary scalp redness, mild itching, or a burning sensation. These localized reactions are usually not severe enough to warrant discontinuation of the treatment.
Current Research Status and Evidence Gap
Scientific support for melatonin’s use in hair growth comes from small-scale clinical trials and observational studies. These investigations report positive outcomes, including improvements in hair density and reduced shedding, particularly in individuals with androgenetic alopecia and diffuse hair loss. For example, one multicenter study noted a decrease in patients experiencing moderate or severe hair loss after three months of topical melatonin use.
A substantial evidence gap remains due to the variability in study design and the limited number of large-scale, randomized, placebo-controlled trials. Larger studies are necessary to establish long-term efficacy and define the optimal concentration and duration of treatment. Furthermore, melatonin is marketed as a cosmetic ingredient or dietary supplement, meaning it has not undergone the rigorous testing required for drug approval by regulatory bodies like the FDA for hair loss treatment.
When compared against established pharmaceutical treatments, such as minoxidil, melatonin is considered a promising adjunctive or alternative option. Its mechanism of action, centering on antioxidant protection and growth cycle support, is distinct from the primary vascular effects of minoxidil. While current evidence supports its potential as a well-tolerated solution, researchers agree that more high-quality evidence is needed to fully integrate topical melatonin into standard treatment protocols.