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

The rosemary essential oil is rich in compounds believed to confer a potent antimicrobial activity, such as rosmarinic acid, carnosol, rosmanol, as well as oxygenated monoterpenes like camphor and borneol. These molecules are thought to act at different levels to disrupt the metabolism, membrane integrity and replication capacity 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, by reducing bacterial growth. This sanitising effect is particularly beneficial for individuals whose scalp becomes greasy quickly and who are prone to dandruff, often associated with an imbalance in the scalp microbiota. By limiting bacterial proliferation, rosemary oil also helps to prevent the blockage of hair follicles, favouring a healthier environment for hair growth.

Beyond its purifying properties, rosemary essential oil is notable for its soothing potential, which is particularly beneficial for sensitive or discomfort-prone scalps. This anti-inflammatory effect is based on the oil’s richness in aromatic compounds, such as eucalyptol (1.8-cineole) and α-pinene. Eucalyptol is thought to be able to modulate the immune response.

A study conducted on rats demonstrated 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 completes the anti-inflammatory profile of rosemary oil by inhibiting a signalling pathway involved in the activation of inflammation-related genes (NF-κB).

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

Among the hair-care virtues attributed to rosemary essential oil, its potential to stimulate hair growth and prevent hair loss is garnering increasing interest. This effect hinges on several mechanisms: a local action on microcirculation, enhancing the delivery of nutrients and oxygen to the hair follicles they require; 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 resulting in progressive hair thinning.

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

An active compound identified in the extract, 12-methoxy-sarcosalic acid, would be partly responsible for this anti-androgenic activity.

Nevertheless, the results in human volunteers are more mixed. In a clinical trial conducted on 100 men suffering from androgenetic alopecia, 10% rosemary essential oil was compared with a 2% minoxidil solution, a drug known to stimulate hair growth. After six months of daily application, no change in hair count was observed in either group. While these findings are surprising for minoxidil—whose efficacy has been demonstrated in numerous other studies—the same was true for the rosemary essential oil.

Despite its promising potential to stimulate hair growth, rosemary essential oil is yet to undergo thorough clinical studies.

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

Antioxidants can help prevent the onset of white hair. Rosemary essential oil fits this rationale thanks to its richness in antioxidant compounds (1,8-cineole, α-pinene and β-pinene). They have demonstrated their ability to scavenge free radicals in numerous studies, thereby limiting their harmful impact on pigment cells. By reducing oxidative stress-related damage, it may thus contribute to slowing the greying of hair.

Although the role of free radicals in hair greying is scientifically established, as are the antioxidant properties of rosemary oil, no study to date has directly demonstrated that this natural ingredient can prevent the formation of white hair.

• SAHEBKAR A. & al. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed (2015).

• HAMIDPOUR S. & al. Rosmarinus officinalis (Rosemary): a novel therapeutic agent for antioxidant, antimicrobial, anticancer, antidiabetic, antidepressant, neuroprotective, anti-inflammatory, and anti-obesity treatment. Biomedical Journal of Scientific & Technical Research (2017).

• GONZÁLEZ-MINERO F. J. & al. Rosmarinus officinalis L. (Rosemary): an ancient plant with uses in personal healthcare and cosmetics. Cosmetics (2020).

• MALVEZZI DE MACEDO L. & al. Rosemary (Rosmarinus officinalis L., syn Salvia rosmarinus Spenn.) and its topical applications: a review. Plants (2020).

• MOLINER C. & al. Rosemary flowers as edible plant foods: phenolic composition and antioxidant properties in Caenorhabditis elegans. Antioxidants (2020).

• NAKAGAWA S. & al. Rosmarinus officinalis L. (Rosemary) extracts containing carnosic acid and carnosol are potent quorum sensing inhibitors of Staphylococcus aureus virulence. Antibiotics (2020).