What are the beneficial effects of rosemary essential oil on hair?

The rosemary essential oil is rich in compounds believed to confer potent antimicrobial activity, such as rosmarinic acid, carnosol, rosmanol, and oxygenated monoterpenes like camphor and borneol. These molecules may act at multiple levels to disrupt the metabolism, membrane integrity, and replicative ability of microorganisms. Studies in vitro have demonstrated that rosemary essential oil inhibits the proliferation of several bacterial strains, notably Escherichia coli and Cutibacterium acnes, bacteria sometimes implicated in certain forms of dermatitis.

Rosemary essential oil would thus help to purify the scalp, reducing bacterial growth. This cleansing effect is particularly beneficial for people whose scalps become oily quickly and who are prone to dandruff, often linked to an imbalance in the scalp microbiome. By limiting bacterial proliferation, rosemary oil also helps reduce hair follicle blockage, promoting a healthier environment for hair growth.

Beyond its purifying properties, rosemary essential oil distinguishes itself by its soothing potential, which is beneficial for the sensitive or discomfort-prone scalps. This anti-inflammatory effect is based on the oil’s richness in aromatic molecules, such as eucalyptol (1,8-cineole) and α-pinene. Eucalyptol is thought to have the ability to modulate the immune response.

A study conducted in rats has shown that this molecule inhibits the production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, etc.) in white blood cells (lymphocytes and monocytes). α-Pinene enhances the anti-inflammatory profile of rosemary oil by inhibiting a signaling pathway involved in the activation of genes responsible for inflammation (NF-κB).

These various effects make rosemary essential oil a valuable natural ingredient for relieving sensations of discomfort associated with scalp imbalance, oxidative stress, or everyday aggressors (pollution, UV rays, hard water, tight hairstyles...). This oil is also valued by individuals with a reactive scalp, or even prone to eczema flare-ups, in addition to a dermatological treatment.

Among the hair benefits attributed to rosemary essential oil, its potential to stimulate hair growth and prevent hair loss is drawing increasing interest. This effect is based on several mechanisms: a local action on microcirculation that enhances the delivery of nutrients and oxygen to the hair follicles, an indirect anti-inflammatory effect on the follicles, and an inhibitory activity on the androgenic pathway involved in hair loss.

Reminder: Androgenetic alopecia is primarily linked to the excessive conversion of testosterone into dihydrotestosterone (DHT) by the 5α-reductase enzyme. DHT binds to hair follicle receptors, disrupting their growth cycle and leading to progressive hair thinning.

Scientists assessed the effect of a hydroalcoholic rosemary extract on this mechanism. In a mouse model of testosterone-induced alopecia, daily application of 2 mg of rosemary extract led to a significant hair regrowth after 16 days of treatment. In vitro, this extract demonstrated marked inhibition of the 5α-reductase enzyme, as well as reduced binding of DHT to its receptors.

An active compound identified in the extract, the12-methoxy-sarcosalic acid, is partly responsible for this anti-androgenic activity.

Nevertheless, the results in human volunteers are more mixed. In a clinical study involving 100 men with androgenetic alopecia, 10% rosemary essential oil was compared to a 2% minoxidil solution, a drug known to promote hair growth. After six months of daily application, no change in hair count was observed in either group. Although the results for minoxidil, whose efficacy has been demonstrated in numerous other studies, were impressive, the same was true for rosemary essential oil.

Despite its promising potential to stimulate hair growth, rosemary essential oil still requires in-depth clinical studies.

The appearance of white hair is a natural phenomenon influenced by genetics and the environment. The oxidative stress plays a key role: with age, especially from around 35, the cells responsible for hair pigmentation become less active. Free radicals accelerate this process by damaging these cells, disrupting melanin production and promoting the progressive emergence of white hair.

Antioxidants can help prevent the appearance of white hair. Rosemary essential oil follows this rationale due to its richness in antioxidant compounds (1,8-cineole, α-pinene, and β-pinene). They have demonstrated their ability to trap free radicals in numerous studies, thereby limiting their deleterious impact on pigment cells. By reducing oxidative stress–related damage, it could thus contribute to slowing down hair whitening.

While the effect of free radicals on hair graying is scientifically established, as are the antioxidant properties of rosemary oil, no study to date has directly demonstrated that this natural ingredient can prevent gray hair.

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