What are the benefits of rosemary essential oil for hair?

Beyond its purifying properties, rosemary essential oil offers soothing potential for the sensitive or discomfort-prone scalps. This anti-inflammatory effect is due to the oil’s richness in aromatic molecules such as eucalyptol (1,8-cineole) and α-pinene. Eucalyptol has been studied for its ability to modulate the immune response. A study in rats showed that this terpene inhibits pro-inflammatory cytokine production (TNF-α, IL-1β, IL-4, and IL-5) in lymphocytes and TNF-α, IL-1β, IL-6, and IL-8 in monocytes. Lymphocytes and monocytes are two types of white blood cells. α-Pinene complements rosemary oil’s anti-inflammatory profile by blocking nuclear translocation of the NF-κB transcription factor, a key pathway in pro-inflammatory gene activation.

These effects make rosemary essential oil a natural ingredient for relieving irritation, itching, or redness linked to scalp imbalance, oxidative stress, or everyday aggressors (pollution, UV radiation, hard water, tight hairstyles). This oil targets individuals with a reactive scalp, or prone to flare-ups of eczema, as a complement to a dermatological treatment.

Rosemary essential oil is linked to hair growth stimulation and shedding prevention. Interest in these effects is growing among men. These effects rely on several mechanisms. A local action on microcirculation delivers nutrients and oxygen to hair follicles. An indirect anti-inflammatory effect protects follicles. An inhibitory effect on the androgen pathway addresses hormonally driven hair loss. Androgenetic alopecia results from excessive conversion of testosterone to dihydrotestosterone (DHT) by the enzyme 5α-reductase. DHT binds to follicle receptors, alters the growth cycle, and causes progressive hair thinning. To counter this process, people often use 5α-reductase inhibitors.

Scientists evaluated the action of a hydroalcoholic rosemary extract on this mechanism. In a mouse model of testosterone-induced alopecia (C57BL/6 mice), application of 2 mg of the extract each day led to a significant hair regrowth after 16 days of treatment, compared with the control group. In vitro, the extract inhibited the 5α-reductase enzyme and reduced DHT binding to its receptors. An active compound identified in the extract, 12-methoxy-sarcosalic acid, is responsible in part for this anti-androgenic activity.

However, results from human volunteers are mixed. In a clinical trial of 100 men with androgenetic alopecia, 10% rosemary essential oil was compared with a 2% minoxidil solution, a treatment known to restore hair growth. After six months of daily application, no change was observed in either group for hair count. These findings contrast with minoxidil’s efficacy shown in multiple other studies and do not demonstrate rosemary’s benefit for hair growth.

Despite its potential to stimulate hair growth, rosemary essential oil requires additional clinical studies.

The gradual emergence of white hair is a complex biological process influenced by genetic and environmental factors. Among these, the oxidative stress plays a key role by targeting melanocytes, the cells that produce melanin. From around age 35, these cells at the base of hair follicles experience a decline in activity, a process accelerated by free radicals. By attacking cellular components, including mitochondrial DNA in melanocytes, free radicals cause mutations that impair mitochondrial function, affecting melanogenesis and precipitating the onset of white hair.

Antioxidants, molecules that neutralize free radicals, play a preventive role in white hair development. Rosemary essential oil fits this approach through its richness in antioxidant compounds, including 1,8-cineole, α-pinene, and β-pinene. These terpenes have demonstrated their ability to trap free radicals in numerous studies, limiting their harmful impact on pigment cells. By preserving melanocyte and mitochondrial integrity, rosemary essential oil may slow hair graying linked to oxidative stress.

This remains a hypothesis. While the role of free radicals in hair graying and the antioxidant properties of rosemary oil are established, no study to date has shown that this natural ingredient can prevent gray hair.