Is it better to use rosemary in shampoo or as a natural oil?

Rosemary (Rosmarinus officinalis), a Mediterranean herb with a long history in natural medicine, has gained significant popularity in hair care. Its presence in shampoos and essential oils is marketed as a solution for strengthening hair and reducing hair loss, making it a star ingredient in hair cosmetics. But how much truth is there to these claims? To understand which of these formulations is more effective, we will analyze both the available scientific evidence and the influence of marketing on its popularity.

Rosemary in hair care: myth or reality?

The promotion of rosemary in hair products is based on its supposed ability to improve blood circulation in the scalp, strengthen hair follicles, and stimulate hair growth. Traditional medicine supports this belief, as rosemary has been used for centuries as a remedy for scalp problems. However, the actual effectiveness of this ingredient depends on several factors, such as its concentration in the product, the frequency of application, and the way it is administered.

Rosemary's antioxidant and anti-inflammatory properties have been studied in the lab, and one small human trial has tested rosemary oil for hair loss. How much of its active compounds reaches the scalp from a shampoo compared with an oil has not been measured.

Rosemary shampoos: marketing or real solution?

Shampoos with rosemary extract are marketed as natural options for improving hair health. Their popularity is largely due to their image as a natural alternative to conventional treatments.

However, the effectiveness of these products has been questioned by experts due to the way they are used. The key to their limited action lies in the short contact time with the scalp, as shampoo is rinsed off after just one or two minutes, reducing the absorption of rosemary's active compounds.

Additionally, many shampoos contain only trace amounts of rosemary extract, suggesting that its inclusion is more about marketing strategies than proven benefits. For an ingredient to have a real impact, it must be applied in adequate concentrations and remain on the scalp long enough to be absorbed.

Strengthening Hair vs. Reducing Hair Loss

In contrast to treatments like minoxidil, whose effectiveness has been supported by multiple clinical studies, rosemary's ability to reach hair follicles has not been measured, and its effect on hair growth rests on one small trial.

While minoxidil works directly on follicles by prolonging the anagen phase of the hair cycle and increasing blood flow in the scalp, rosemary's absorption and mechanisms have hardly been studied. Additionally, the dosage and application frequency of minoxidil are clearly established in clinical studies, whereas the use of rosemary still lacks a consensus on the ideal concentration for optimal benefits.

According to dermatologists, shampoos primarily serve a cleansing function, and while some ingredients may provide additional benefits, the absorption of active compounds is minimal compared to other formats. Moreover, many commercial shampoos contain only small amounts of rosemary extract, reinforcing the idea that its inclusion in these products is more related to marketing strategies than to scientifically proven benefits.

A study published in Skinmed in 2015 compared rosemary oil with 2% minoxidil in patients with androgenetic alopecia.

Panahi and colleagues (Skinmed, 2015; PMID 25842469) randomised 100 people with androgenetic alopecia to rosemary oil or 2% minoxidil for six months. Neither group’s hair count changed significantly at three months; both rose significantly from baseline at six months, with no significant difference between the groups. Scalp itching increased in both groups and was more frequent with minoxidil. There was no placebo arm, the comparator was the weaker 2% strength, and the trial has not been independently replicated, so it cannot show that rosemary oil is as effective as minoxidil.

This study used a leave-on rosemary oil, not a shampoo. It says nothing directly about rinse-off products; a shorter contact time may mean less effect, but no study has tested this.

Rosemary oil: a more potent option?

It is assumed that rosemary oil left on the scalp is absorbed better than a rinse-off product, but this has not been measured. It has been suggested that this oil may stimulate hair growth by improving scalp microcirculation and providing antioxidant compounds that protect hair follicles.

A 2013 study published in Phytotherapy Research analyzed the effects of rosemary extract on the inhibition of 5-alpha reductase, the enzyme responsible for converting testosterone into dihydrotestosterone (DHT), a key factor in hair loss. The extract inhibited this enzyme in the test tube and improved hair regrowth in mice given testosterone (Murata et al. 2013). However, this study was conducted on animal models and in vitro cells, so further research in humans is needed to confirm these findings.

Safety. Rosemary essential oil is concentrated. Poison Control advises diluting essential oils in a carrier oil before they touch the skin, not using them on damaged skin, and stopping if a rash appears (National Capital Poison Center). Allergic contact dermatitis to rosemary has been reported (Serra et al. 2005). Rosemary oil is not for swallowing: some essential oils are poisonous if swallowed, and children are more susceptible, so keep bottles out of their reach (National Capital Poison Center). The EU herbal medicines committee does not recommend rosemary oil products for people under 18 or during pregnancy or breastfeeding, because safety has not been established, and advises keeping it away from the eyes (EMA, 2024). No study has established a dilution or schedule for hair.

User Experiences

Community feedback on the effectiveness of rosemary for hair loss suggests that using it as a natural oil may be more beneficial than incorporating it into shampoo. Many users on the r/tressless forum reported that applying rosemary oil directly to the scalp allowed for better absorption, as it had more time to interact with the hair follicles compared to being briefly rinsed out in shampoo. Several individuals who used diluted rosemary essential oil with a carrier oil, such as coconut or jojoba oil, mentioned seeing improvements in hair thickness and reduced shedding over time. Some even incorporated microneedling into their routine to enhance penetration, believing this helped maximize rosemary oil’s effectiveness.

On the other hand, users who used rosemary-infused shampoo generally found it to be a convenient option but were divided on its results. Some believed it contributed to scalp health and improved circulation, but others felt that since the shampoo was washed out quickly, the rosemary had little time to exert its potential benefits. A few users suggested leaving the shampoo on the scalp for a few minutes before rinsing to increase its effectiveness, while others combined both approaches—using rosemary oil treatments a few times a week while also using a rosemary-infused shampoo for maintenance.

There were also discussions about irritation and sensitivity. A small number of users reported scalp irritation from undiluted rosemary essential oil, emphasizing the importance of proper dilution. In contrast, rosemary shampoo was generally tolerated well, but some noted that commercial formulations might contain additional ingredients that could counteract rosemary's natural benefits.

Overall, members leaned toward using rosemary oil directly on the scalp, believing it gives better absorption, with rosemary shampoo as a supplementary option; absorption from either form has not been measured.

Conclusion: Which to Choose?

No study has compared rosemary oil with rosemary shampoo, and the evidence for either is limited. The choice between the two depends on individual needs and patience in applying the treatment. Neither form has been shown to treat hair loss.

It is important not to be swayed solely by marketing strategies and to pay attention to ingredient concentrations in chosen products. In any case, consulting a dermatologist remains the best option to determine which treatment is most suitable based on hair type and individual conditions.

References

Panahi, Y., Taghizadeh, M., Marzony, E. T., & Sahebkar, A. (2015). Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: A randomized comparative trial. Skinmed, 13(1), 15-21. Retrieved from https://pubmed.ncbi.nlm.nih.gov/25842469/

Murata, K., Noguchi, K., Kondo, M., Onishi, M., Watanabe, N., Okamura, K., & Matsuda, H. (2013). Promotion of hair growth by Rosmarinus officinalis leaf extract. Phytotherapy Research, 27(2), 212-217. https://doi.org/10.1002/ptr.4712. Retrieved from https://pubmed.ncbi.nlm.nih.gov/22517595/

Serra, E., Vila, A., Peramiquel, L., Dalmau, J., Granel, C., & Alomar, A. (2005). Allergic contact dermatitis due to rosemary. Contact Dermatitis, 53(3), 179-180. Retrieved from https://pubmed.ncbi.nlm.nih.gov/16128769/

European Medicines Agency, Committee on Herbal Medicinal Products (2024). European Union herbal monograph on Rosmarinus officinalis L., aetheroleum (EMA/HMPC/513893/2021, Revision 1). Retrieved from https://www.ema.europa.eu/en/medicines/herbal/rosmarini-aetheroleum

National Capital Poison Center. Essential oils: Poisonous when misused. Retrieved from https://www.poison.org/articles/essential-oils

El País. (December 13, 2024). "The tricks that actually stop hair loss in women." Retrieved from https://elpais.com/salud-y-bienestar/2024-12-13/tengo-la-casa-llena-de-pelos-y-es-horroroso-los-trucos-que-si-frenan-la-caida-capilar-en-mujeres.html

AS. (December 7, 2024). "If you have this 'sacred herb' in the kitchen, you have a treasure: it improves digestion, strengthens hair, and reduces stress." Retrieved from https://as.com/tikitakas/estilo/si-tienes-esta-hierba-sagrada-en-la-cocina-tienes-un-tesoro-mejora-la-digestion-fortalece-el-pelo-y-reduce-el-estres-n/