Rosemary Oil Has 1.3 Billion Views on #Hairtok. But Is It Really Effective? A Dermatologist Explains

Another day, another TikTok trend. In the latest frenzy, the app is rife with people raving about the benefits of rosemary oil for hair growth. From working wonders after chemotherapy to addressing baldness and being the secret to envious locks, the botanical has racked up some good press—and the endorsement of some medical and hair professionals. But after diving into the oft-cited study used to back up the science behind this ingredient, and speaking with a dermatologist and trichologist, it turns out that rosemary oil might not be as effective as you think. From dandruff to hair loss, here’s what it really can—and can’t—do.

• Dr. Ryan Turner is a board-certified, New York City-based dermatologist who specializes in cosmetic, general and surgical dermatology, and is the founder of TRNR Skin. Turner is also an assistant professor at the Albert Einstein College of Medicine and the former director of dermatologic and laser surgery at Montefiore Medical Center. Dr. Turner received his medical degree from Harvard Medical School.

• Shann Christen is a trichologist, founder of BioMethod and owner of Shann Christen Studio Salon in Los Angeles. Christen has over 20 years of experience in the hair care industry, including 12 of which he spent on advanced studies in Italy. At his salon, Christen provides hair analysis and advanced hair treatments.

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There’s a popular study that serves as the primary citation for many people’s claims that rosemary oil can stimulate hair growth. It’s a 2015 paper published in SKINMed, a peer-reviewed dermatological journal. The abstract claims that rosemary oil is just as effective as minoxidil (a typical medication prescribed for hair loss) in encouraging hair growth. Closer inspection of the results, however, reveals that they are rather underwhelming.

“The significant difference was found between the study groups regarding hair count either at month three or month six,” the authors write. While that could mean rosemary oil held its own, there are a few important factors to consider.

For one, study participants—all male—were prescribed 2 percent minoxidil to treat androgenetic alopecia, also known as male/female pattern baldness.

“Typically, 5 percent [minoxidil] is recommended for male pattern hair loss, [while women are prescribed] 2 percent,” Dr. Turner explains. So, while the dosage in this study is not incorrect, it’s not optimized. According to Dr. Turner, minoxidil is a blood pressure medication, and men typically have a higher tolerance to it. Absorbing too much through the scalp can affect your blood pressure.

“Minoxidil works to increase blood flow to an area of hair loss,” he says. “It dilates or expands the blood vessels, and that increases oxygen and nutrients into the base of a hair follicle.”

This makes the medication effective when treating many different types of hair loss, including autoimmune hair loss engendered by lupus and alopecia areata, an autoimmune condition that leads to sudden patches of hair loss. While one could extrapolate the results of the study to female pattern baldness, Dr. Turner cautions that there isn’t any data that would allow the results to be applied to the two former types of hair loss. So, even if rosemary oil holds up to minoxidil, whether it works for you depends on your condition.

“What’s difficult to interpret is how effective rosemary oil really is, because when you look at the numbers in terms of average hair count, it was very minimal—we’re talking a few hairs,” Dr. Turner says. Further delving into the results shows comparison bar graphs that pretty much flatline. There are also other variables that are unclear, including the scalp surface area studied.

“At best, this article suggests that there can be some component of rosemary oil that could support hair and make it thicker, but we don’t know that it necessarily allows for a robust stimulation of new hair growth from baseline,” Dr. Turner says. “We need more research to discover if rosemary oil [and other] botanical-based products can really regrow hair.”

While the study isn’t conclusive, Dr. Turner and Christen say that there are some benefits that hold up to science. “Rosemary oil contains glycolic acid, flavonoids, saponins and bitter substances, which have an antioxidant, antibacterial, astringent and toning action that [promotes] the well-being of the skin, stimulate the microcirculation and improve oxygenation at the root to strengthen the hair,” Christen explains.

Stimulate Circulation

Rosemary oil contains rosmarinic acid, among other phytochemicals known as terpenes. Terpenes, Dr. Turner explains, can increase blood flow. “There may be some interaction with the nerve cells that control the blood vessels. It relaxes them in the same way that minoxidil will relax blood vessels to increase oxygen and nutrients,” he elaborates.

When you increase blood flow to your scalp, this allows your hair to receive more nutrients and oxygen. Dr. Turner likens your scalp to a garden: If you don’t “water” it enough, nothing will grow. However, this isn’t specific to rosemary oil; there are many ways to increase circulation, including a good ol’ fashioned head massage.

Strengthen Hair Structure

“Rosemary oil strengthens the structure of the hair, preventing breakage and brittleness,” Christen says. Dr. Turner notes that there’s no evidence that rosemary oil can rectify damaged keratin, but says it’s reasonable that rosemary oil can support healthier hair—mainly for the reasons listed above.

Regulate Sebum

According to Christen, excess sebum can lead to premature hair loss (a common effect of seborrheic dermatitis). Rosemary oil can help regulate and balance sebum production, but Dr. Turner says that this is a trait of most botanicals. Many botanicals, including, tea tree oil and aloe vera, contain antioxidants that are astringent, meaning it causes skin cells to contract, which helps with oil regulation.

If used properly, rosemary oil shouldn’t cause irritation, however, Christen notes that skin irritation and contact dermatitis could occur. “It is advisable not to use rosemary essential oil [if you are sensitive to it or its components], have epilepsy, hypertension or are pregnant,” he says.

Rosemary oil contains terpenes, which in addition to stimulating circulation, also have antimicrobial properties. Dandruff, Dr. Turner explains, isn’t just caused by a dry scalp—sometimes it’s caused by a yeast fungus called Malassezia.

“If you reduce the amounts of yeast on the scalp, you reduce inflammation and flaking,” he says, adding that shampoos like Selsun Blue and Head and Shoulders have anti-yeast properties.

Meanwhile, antioxidants in rosemary oil can help reduce inflammation in the scalp, while glycolic acid can aid with skin cell turnover. However, if a patient wants a natural remedy, Dr. Turner will recommend tea tree oil over rosemary.

Both Christen and Dr. Turner stress that you shouldn’t use pure rosemary oil as it can lead to irritation.

“It is preferable to mix [a few drops] with shampoos, scalp masks, spray lotions, etc.,” Christen advises. He uses many products from the Italian brand Esterel Beauty on many clients, including the Detoxinant Fluid, Atone Fluid and Sec Fluid for the prevention of abnormal hair loss or for specific alopecias, and Fluide Relaxant for dandruff, dermatitis and itching.

All that goes to say is, if you’re dealing with hair loss, get yourself to a dermatologist first, take their advice and use rosemary oil and its related products as a supplement on top of authorized treatment.