Before diving into the benefits, you should know that the exact science behind melatonin and hair growth isn’t fully understood. “Melatonin is critical for a healthy follicle,” says Alan Meyers, senior vice president and chief scientific officer at MONAT, but researchers are still trying to determine why 1topical melatonin can promote hair growth1; that being said, there have been some studies with noteworthy results.
“A number of clinical studies have been done showing some improvement in androgenic alopecia2 in men and women after applying topical melatonin at night,” explains board-certified dermatologist Cynthia Bailey, M.D., founder of DrBaileySkinCare.com. (Androgenic alopecia, if you’re unfamiliar, is commonly referred to as male- or female-pattern baldness.) “It works particularly well in women, perhaps due to melatonin’s ability to modify the hair follicle response to estrogen3.”
A recent 2022 in vitro study also found that melatonin can signal human dermal papilla cells4 (aka, cells found at the bottom of hair follicles that play a role in hair growth), which may be able to explain its positive effects.
Finally, “Melatonin reduces free radical stress3 at the follicle level that can lead to reduced hair growth,” Bailey adds. After all, oxidative stress plays a major role in hair loss5, as the accumulation of free radicals over time can cause the follicle to close off, which limits growth and can eventually lead to shedding. That’s why experts tell you to tend to your scalp with antioxidants to fend off those free radicals—and melatonin does function as a powerful antioxidant.
Science jargon aside, we can likely assume that melatonin can lead to hair growth benefits when applied topically—even if we don’t know exactly why.