Quick answer: the evidence for rosemary oil and hair growth is promising but thin. One small 2015 trial found that, after six months, rosemary oil increased hair count in people with pattern hair loss about as much as a low-strength (2%) minoxidil solution, with less scalp itching. But that is one study, without a placebo group, and it hasn't been confirmed by larger trials. Rosemary oil isn't proven to regrow hair, make healthy hair grow faster or work in weeks. If you want to try it, dilute it, patch test first and give it at least six months. For sudden or patchy hair loss, see your GP.
Rosemary oil has become one of the most talked-about hair products on social media, with videos promising thicker, faster-growing hair. We get asked about it all the time, so we went back to the actual research to separate what's been shown from what's been hyped.
What the research actually shows
There are only a handful of studies, and they're often quoted as if they prove more than they do. Here are the ones that matter.
1. The 2015 rosemary oil vs minoxidil trial
This is the study behind most of the headlines. Researchers randomly assigned 100 adults with androgenetic alopecia (pattern hair loss) to use either rosemary oil or minoxidil 2%, a licensed hair-loss treatment, for six months.
- At three months: neither group saw a significant change in hair count.
- At six months: both groups had a significant increase in hair count, with no significant difference between them.
- Side effects: scalp itching increased in both groups, but was more common with minoxidil.
What it doesn't show: there was no placebo group, so we can't tell how much of the change was down to the oil itself. The comparison was with 2% minoxidil, a lower strength than the 5% often used for men. It's a single, fairly small study that hasn't been repeated at scale, and the published summary doesn't say how big the increase was.
2. The 1998 aromatherapy study
In a seven-month trial, 86 people with alopecia areata (an autoimmune condition that causes patchy hair loss) massaged their scalp daily with either a blend of thyme, rosemary, lavender and cedarwood essential oils in jojoba and grapeseed oil, or the carrier oils alone. 44% of the essential oil group improved, compared with 15% of the carrier oil group.
What it doesn't show: rosemary was one of four oils, so the result can't be credited to rosemary alone. Alopecia areata is also a different condition from everyday shedding or thinning.
3. The 2013 mouse study
Lab research found that a compound in rosemary leaf extract blocked 5-alpha-reductase, an enzyme linked to pattern hair loss, and promoted hair regrowth in mice.
What it doesn't show: this was a leaf extract, not the essential oil you buy in a dropper bottle, and it was tested on mice. Results in animals often don't carry over to people.
4. What reviews conclude
A 2025 review of herbal remedies for hair loss in Skin Appendage Disorders described rosemary oil as an attractive option, but noted that the evidence is preliminary: studies are small, short and lack long-term follow-up, and more research is needed to confirm the results and work out how best to use it.
What rosemary oil can and can't do
- Can it help with pattern hair loss? Possibly, modestly, over six months or more, based on one trial. Not proven.
- Can it regrow hair on bald patches? There's no good evidence that it can.
- Will it make healthy hair grow faster or longer? No study has shown this. The research looked at people with hair loss, not people wanting longer hair.
- Will it work in a few weeks? No. Even in the positive trial, there was no measurable change at three months.
- Is it a replacement for medical treatment? No. If you're losing hair, get the cause checked first.
- Does rosemary have a place in scalp care? Yes. Rosemary extract is a common ingredient in scalp care products, used for a fresh, clean-feeling scalp.
Rosemary in our products
We use organic rosemary extract, alongside organic thyme and sage extracts, in our Clarifying range for a flaky scalp: Purifying Shampoo, an anti-dandruff shampoo with tested efficacy against dandruff, and the leave-on Purifying Scalp Treatment, which helps minimise visible dandruff. To be clear, these are scalp care products for dandruff, not hair growth treatments. Read more about what causes dandruff and how to treat it.
How to use rosemary oil safely
If you'd like to try it, these steps keep the risk of irritation low:
- Never apply it neat. Essential oils are concentrated and can irritate the skin. Mix a few drops into a carrier oil such as jojoba.
- Patch test first. Apply a small amount to the inside of your arm and wait 24 to 48 hours. Stop if you get redness, itching or a rash.
- Massage it into the scalp, not the lengths, then wash it out with shampoo.
- Keep it away from your eyes, and away from children's faces.
- Be patient. Give it at least six months before judging, and take photos in the same light so you can compare honestly.
Who should check first: aromatherapy safety guidance advises avoiding some types of rosemary oil in pregnancy and breastfeeding, and for people with epilepsy or high blood pressure. If any of these apply to you, or you take regular medication, speak to your pharmacist or GP before using it.
When to see your GP
See your GP if your hair loss is sudden, comes out in patches or clumps, or comes with an itchy, sore or burning scalp, or if you're simply worried. Hair loss can have many causes, and some are treatable once you know what's behind them. A trichologist can also help with hair and scalp concerns.
Frequently asked questions
Does rosemary oil regrow hair?
It hasn't been proven to. One small trial found an increase in hair count after six months in people with pattern hair loss, similar to 2% minoxidil, but it had no placebo group and hasn't been confirmed by larger studies.
Is rosemary oil as good as minoxidil?
In that one trial, it performed similarly to 2% minoxidil over six months. That's not enough to say it's as effective as minoxidil in general, and minoxidil is a licensed treatment with far more evidence behind it.
How long does rosemary oil take to work?
In the 2015 trial, there was no measurable change at three months; the increase was seen at six months.
Can I leave rosemary oil in overnight?
Some people do, diluted in a carrier oil, then wash it out the next morning. If your scalp feels itchy or irritated, wash it out and stop using it.
Does rosemary water work for hair growth?
We haven't found any clinical studies on rosemary water for hair growth. The research above used rosemary essential oil, an oil blend or a leaf extract.
Will rosemary oil make my hair grow faster?
There's no evidence it speeds up growth in healthy hair. The studies looked at people with hair loss.
Sources
- Panahi Y, et al. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed, 2015. PubMed
- Hay IC, et al. Randomized trial of aromatherapy: successful treatment for alopecia areata. Archives of Dermatology, 1998. PubMed
- Murata K, et al. Promotion of hair growth by Rosmarinus officinalis leaf extract. Phytotherapy Research, 2013. PubMed
- Ahmed A, et al. Herbal Remedies for Hair Loss: A Review of Efficacy and Safety. Skin Appendage Disorders, 2025. Karger
- International Federation of Aromatherapists. Contraindications in Aromatherapy Guidelines. IFA
This article is for general information and isn't medical advice.
About the author
Charlotte Read has spent six years in the hair industry with Insight Professional and holds a First Class BSc in Business Management and Marketing. She writes with reference to real salons across social media and the wider Insight community, and draws on the Insight office team, who between them bring over 100 years of combined experience on salon floors.
Where technical expertise is needed, Charlotte consults Lorraine Matic, Head of Insight UK Education, who brings over 38 years of global experience in colour, technique and hair science.