More than most natural remedies: one randomized trial of 100 people found rosemary oil matched minoxidil 2% - both groups gained hair count significantly at six months, with no significant difference between them and less itching on rosemary.
The honest frame: a single trial, never replicated at scale, against the weaker OTC minoxidil strength. Interesting is not proven. Best-evidenced remains minoxidil and finasteride; rosemary is a cheap, safe addition if you dilute it, use it daily, and judge at six months. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Does rosemary oil work for hair growth?
More than most natural remedies - there is one real randomized trial, and it is the entire evidence base. The 2015 trial randomized 100 people with androgenetic alopecia to rosemary oil or minoxidil 2% for six months: at three months neither group had gained hair count, at six months both groups showed a significant increase, and there was no significant difference between them - with less scalp itching on rosemary than minoxidil. That is genuinely interesting. The honest frame: it is a single trial, never replicated at scale, testing a specific oil preparation against the weaker over-the-counter minoxidil strength - "matched one small study once" is not "proven." So the practical ranking: if you are losing hair and want the best-evidenced treatments, that is still minoxidil and finasteride with a clinician; if you want to try rosemary oil, it is cheap and safe, apply it diluted to the scalp daily, and judge at six months with photos - the trial clock, not the TikTok clock. Shedding that continues for months deserves a diagnosis first - pattern loss, thyroid, iron, and telogen effluvium all look similar from the drain.