Peppermint vs Rosemary Oil for Hair: What Two Studies Compared
The two studies that get quoted whenever peppermint and rosemary are compared for hair are not the same kind of study, and putting them in one chart makes the comparison look fairer than it is. The peppermint paper is about shaved mice. The rosemary paper is about 100 people. Neither is a reason to put an essential oil on your scalp in place of seeing someone about hair loss, and we sell peppermint oil, not rosemary and not a hair product.
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Shop Now →The two studies side by side
| Peppermint (Oh et al., 2014) | Rosemary (Panahi et al., 2015) | |
|---|---|---|
| Who or what | Male C57BL/6 mice, shaved on the back | People with androgenetic alopecia |
| Groups | Saline, jojoba oil, 3% minoxidil, 3% peppermint oil in jojoba | Rosemary oil (n = 50) vs 2% minoxidil (n = 50) |
| Numbers | 5 mice per group for the growth scoring; 3 to 5 per group for tissue measures | 100 participants |
| Duration | 4 weeks, 100 microlitres once daily, 6 days a week | 6 months, visits every 3 months |
| Reported result | About 92% growth with peppermint vs about 55% with minoxidil at week 4 (scored on a 0 to 5 scale) | No significant difference in hair count between groups at 3 or 6 months; both rose significantly by month 6 |
| Side effects reported | No differences in body weight, food or water intake; no skin or organ assessment reported | Scalp itching rose in both groups, more with minoxidil |
| Design | Randomised groups | Randomised, single-blind |
Sources: Oh, Park and Kim, Toxicological Research, 2014; Panahi et al., Skinmed, 2015 (abstract only). The rosemary abstract does not state the oil concentration, so we cannot tell you what was applied.
Reading the mouse study without overreading it
The mice were shaved on a 2 by 4 cm patch of the back, and hair "growth" was a score of how far the patch had filled in. That matters. As we read it (our reasoning, not the authors' statement), a shaved-patch model measures how quickly regrowth fills in, not whether a thinning human scalp reverses. The authors diluted a French peppermint oil (reported as menthol 42.34%, menthone 19.39%, menthofuran 3.92%) to 3% in jojoba oil. Our arithmetic on their dose: 100 microlitres of a 3% solution is 3 microlitres of oil, or 0.06 of a drop at 20 drops per ml, spread over 8 cm2. A human scalp, a human hair cycle and a human dose per area are all different, and the paper offers no way to convert between them.
The paper also has features a careful reader should weigh. Only five mice per group were scored for growth, and the tissue measurements used three mice per group at some time points. The text says the peppermint group was "comparable to" minoxidil on a marker and elsewhere says it did "better," which is internally inconsistent. The toxicity check in the title is based on body weight and food intake, not on skin or organs. The proposed mechanism, better blood supply to the hair papilla, was not measured. And the concentration (3%) is higher than the 2% top of our own copy, so the paper cannot be used to justify what we tell customers to do.
The Cosmetic Ingredient Review panel's 2018 re-review of peppermint ingredients cites the same mouse paper in its safety assessment (CIR, 2018) as a finding that peppermint oil "facilitates hair growth" in mice; its conclusion that the oil is safe in cosmetics "when formulated to be non-sensitizing" is about cosmetic use, not about hair loss.
Reading the rosemary trial without overreading it
This one is a human trial, which is why it is the stronger of the two. It is also modest. Fifty people per arm, single-blind, six months, hair counted by standardised photomicrography. Nothing changed at three months; both groups improved by six. The authors concluded the results support rosemary oil's efficacy, but the evidence is that two groups ended up statistically indistinguishable, not that rosemary outperformed anything, and there was no group using neither treatment, so the trial cannot say how much of the change would have happened anyway. Scalp itching was reported to rise in both arms. We are quoting the abstract; we have not read the full text.
Where the "essential oils and hair" claim really comes from
A third study is often folded in with these: Hay, Jamieson and Ormerod (Arch Dermatol, 1998). It randomised 86 people with alopecia areata, a different diagnosis from the androgenetic alopecia in the rosemary trial. The active group had a daily scalp massage with thyme, rosemary, lavender and cedarwood oils in jojoba and grapeseed carriers; controls had the carrier oils only. After seven months, 19 of 43 (44%) in the active group improved against 6 of 41 (15%) in the control group (P = .008). Peppermint was not in the blend. Its relevance to a bottle of peppermint is nil, and its relevance to rosemary is limited to rosemary being one of four oils in one blend for one condition.
The legal line that shapes this page
The FDA says a product's status as a cosmetic or a drug "is determined by a product's intended use," and lists claims such as "restore hair growth" among those that make a product a drug (FDA). That is why neither this page nor our product pages say that our oils grow, thicken or restore hair. We report what two papers measured. Our own shop copy lists peppermint for fragrance uses, and our distillation page says "we make no medical claims."
What we recommend, and what we do not
- If you are losing hair: the cause decides the treatment, and the cause needs a clinician. A dermatologist is the right first call, especially for patches, sudden shedding or scalp changes. Neither oil is a substitute for a diagnosis.
- If you want peppermint in a scalp product for the tingle: that tingle is a sensation, not a sign anything is working; our dandruff article goes through the same problem for flaking. Dilute first. Our copy says 0.5% to 2% in a carrier and a patch test; for scalp and face we recommend the low end, 0.5% to 1%, because menthol irritates. CIR reports a highest cosmetic use concentration of 5% (2017) and a 5.4% dermal maximum attributed to Tisserand and Young (read second-hand through CIR). Both are above our 2%, and neither is a target.
- Rosemary: we do not sell it. If you want it, buy from a supplier who publishes the species and chemotype, and check that supplier's own safety sheet.
- Eyes, children, pets: keep it away from eyes; keep it off the faces of infants and young children; the existing scalp routine post and dilution guide carry the handling steps.
The two oils we sell are Mentha piperita and Mentha arvensis (cornmint). The mouse paper used a piperita oil with a reported composition; the GC-MS report we publish is for our arvensis oil and gives only chemical-family totals, and our published certificate is a refractive index for a piperita sample. Neither document tells you whether our oils resemble the oil in the paper, so none of this should be read as saying our oils would do what it reports.
For a fuller view of what peppermint can and cannot be credited with, see benefits, honestly.
Peppermint Essential Oil
Peppermint Essential Oil from our own shop, in sizes from 0.5 oz to bulk.
From $10.99
Shop Now →Sources & Further Reading
- Oh JY, Park MA, Kim YC, 2014. Peppermint oil promotes hair growth without toxic signs. Toxicol Res 30:297-304. pmc.ncbi.nlm.nih.gov/PMC4289931
- Panahi Y, Taghizadeh M, Marzony ET, Sahebkar A, 2015. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed 13:15-21. pubmed/25842469
- Hay IC, Jamieson M, Ormerod AD, 1998. Randomized trial of aromatherapy: successful treatment for alopecia areata. Arch Dermatol 134:1349-1352. pubmed/9828867
- Cosmetic Ingredient Review, 2018. Amended Safety Assessment of Mentha piperita (Peppermint)-Derived Ingredients as Used in Cosmetics. cir-safety.org/pepper032018rep.pdf
- US FDA. Is it a cosmetic, a drug, or both? (Or is it soap?) fda.gov/cosmetics