Spray rosemary water on the roots of your hair: what the 2015 study behind the trend actually tested

It has been all over social media for a few years: a bottle of home-brewed rosemary water, sprayed on the scalp to slow hair loss and boost growth. Now the idea is circulating again with an autumn twist.

Behind many of those rosemary claims sits one clinical trial from 2015. The result is often shortened online to “rosemary works as well as minoxidil.” The study itself tells a more complicated story than what TikTok users with spray bottles of homemade rosemary water are claiming.

The study everyone quotes

Researchers led by Yunes Panahi randomly assigned 100 patients with androgenetic alopecia, better known as pattern hair loss, to either rosemary oil or 2% minoxidil. There were 50 people in each group, and researchers checked their hair after three and six months.

At three months, neither treatment had produced a statistically significant increase in hair count. By six months, hair counts had risen significantly in both groups compared with the start of the study. Researchers found no statistically significant difference in hair count between the two groups. Scalp itching occurred in both groups but was reported more often with minoxidil.

That finding is interesting, but it does not prove that rosemary is generally equivalent to minoxidil. It was one relatively small trial, involving one specific type of hair loss and comparing rosemary oil with 2% minoxidil.

Rosemary water is a different product

This is where the social-media version gets ahead of the science. The researchers tested rosemary oil, not rosemary leaves steeped or boiled in water.

The two preparations are chemically different. You cannot assume that spraying homemade rosemary water onto the scalp delivers the same compounds, at the same concentration, as the product used in the trial.

Also, there was no sign of significant improvement after three months. Anyone trying rosemary oil on the basis of this research should therefore know that the study's positive result appeared only at the six-month assessment.

Not every kind of hair loss is the same

The trial concerned androgenetic alopecia. In men, this commonly causes receding temples and thinning around the crown. In women, it more often causes gradual thinning around the top or parting.

Suddenly finding much more hair in the shower can have completely different causes. Normal causes for heavier shedding include stress, fever, illness, weight loss, surgery, childbirth, and low iron.

That distinction matters: a rosemary treatment studied for hereditary pattern loss cannot automatically be expected to help hair shedding caused by illness, medication or another condition.

If you still want to try rosemary

The evidence is limited, but rosemary oil can be tried cautiously as part of a hair-care routine. Experts recommend diluting rosemary oil with a carrier oil such as coconut or jojoba oil rather than applying large amounts of concentrated essential oil directly to the scalp. Testing a small area first can also help identify irritation.

Stop if the scalp becomes red, painful, itchy, or starts burning. And don't expect a quick change: the 2015 trial saw no significant improvement at three months.

You can still use rosemary water if you enjoy it as a scalp or hair rinse. Just don't treat it as a proven hair-growth remedy — that particular preparation has not been established by the study everyone cites.

When hair loss needs a doctor

Contact your GP if you suddenly develop bald patches, lose much more hair than usual, notice continuing thinning or are worried about what is causing it. Make an appointment for sudden bald patches or substantial hair loss, while every expert would advise finding out the cause before turning to commercial hair-loss treatments.

Rosemary may be worth discussing if you have pattern hair loss. But the first question should not be “Does rosemary work?” It should be: What kind of hair loss am I actually dealing with?