Rosemary

Western herbalists class rosemary as a circulatory stimulant, nervine, carminative and mild antispasmodic. It has been used to move blood to the head and limbs, for headaches, migraine and faintness, for nerve pain such as intercostal neuralgia, and for low mood linked to exhaustion ^{22Reference 22Ghasemzadeh Rahbardar et al. · 2020ReviewTherapeutic effects of rosemary (Rosmarinus officinalis L.) and its active constituents on nervous system disorders — reviewView study →}.

Its digestive use is long-standing. The leaf and oil are taken for wind, indigestion and mild cramping of the gut.

European herbal medicine also uses the leaf in baths for aching muscles and joints and for poor circulation in the limbs. The European Medicines Agency recognises both the digestive and the bath uses as traditional ^{28Reference 28European Medicines Agency · 2024ReviewEuropean Union herbal monograph on Rosmarinus officinalis L., folium — Final, Revision 1 (EMA/HMPC/513940/2021) — regulatory monograph. https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-rosmarinus-officinalis-l-folium-revision-1_en.pdfView study →}.

Rosemary’s antioxidant activity rests on its non-volatile diterpene phenols — carnosic acid and carnosol — plus rosmarinic acid and ursolic acid. These are the actives in the standardised rosemary extracts used industrially as food and cosmetic antioxidants ^{1,26Reference 1Satyal et al. · 2017In vitroChemotypic Characterization and Biological Activity of Rosmarinus officinalis — in vitroView study →Reference 26Birtić et al. · 2015ReviewCarnosic acid — reviewView study →}.

Carnosol and carnosic acid inhibit lipid peroxidation more strongly than propyl gallate and scavenge peroxyl and hydroxyl radicals. In one assay, the bleomycin test, both also increased DNA damage, a pro-oxidant effect ^{27Reference 27Aruoma et al. · 1992In vitroAntioxidant and pro-oxidant properties of active rosemary constituents: carnosol and carnosic acid — in vitroView study →}.

Much of the activity is now thought to run through the Nrf2 antioxidant response rather than direct radical scavenging alone ^{26Reference 26Birtić et al. · 2015ReviewCarnosic acid — reviewView study →}.

Almost all of this work is in cells or in food systems. Direct measures of antioxidant benefit in people taking rosemary at realistic oral doses are scarce.

This indication is for the topical oil, not the herb taken by mouth. A 6-month randomised trial in 100 people with androgenetic alopecia (50 per arm) compared rosemary oil with 2% minoxidil. Neither group gained hair at 3 months. Both gained a significant amount by 6 months, with no difference between them, and scalp itching was less frequent with rosemary ^{2Reference 2Panahi et al. · 2015RCTRosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trialView study →}.

A 2025 double-blind trial in 90 adults compared two rosemary blends, rosemary-lavender and rosemary-castor oil, with coconut oil over 90 days. Both rosemary blends improved hair growth rate, thickness and density more than coconut oil. The trial was funded by the product’s maker ^{3Reference 3Patel et al. · 2025RCTRosmagain™ as a Natural Therapeutic for Hair Regrowth and Scalp Health: A Double-Blind, Randomized, Three-Armed, Placebo-Controlled Clinical Trial — RCTView study →}.

The proposed mechanism is better blood flow in the small vessels of the scalp ^{2Reference 2Panahi et al. · 2015RCTRosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trialView study →}.

⚠ The pivotal trial had no placebo arm, the samples are small, and “rosemary oil” formulations differ between studies.

Gap: only one active-comparator RCT with no placebo arm; blends muddy attribution to rosemary specifically, and durability beyond 6 months is untested.

Rosmarinic acid and the diterpenes carry most of the anti-inflammatory activity. Across arthritis, colitis and atopic-dermatitis models, rosmarinic acid suppresses NF-κB signalling and downstream mediators such as TNF-α, IL-1β, IL-6 and COX-2 ^{12Reference 12Luo et al. · 2020ReviewA Review of the Anti-Inflammatory Effects of Rosmarinic Acid on Inflammatory Diseases — reviewView study →}. Carnosic acid suppresses the NLRP3 inflammasome in a mouse model of alcoholic liver injury ^{14Reference 14Zuo et al. · 2023AnimalCarnosic acid suppressed the formation of NETs in alcoholic hepatosteatosis based on the P2X7R-NLRP3 axis — mouseView study →}.

Leaf essential oils from Algeria inhibited the inflammatory enzyme lipoxygenase in vitro, and their composition varied widely from sample to sample ^{13Reference 13Bekhechi et al. · 2024In vitroChemical Variability and Anti-Inflammatory Activity of Rosmarinus officinalis LView study →}.

Human trials of rosemary as an anti-inflammatory are essentially absent ^{12Reference 12Luo et al. · 2020ReviewA Review of the Anti-Inflammatory Effects of Rosmarinic Acid on Inflammatory Diseases — reviewView study →}.

Rosemary’s “herb of remembrance” reputation has been tested in several small human trials, with mixed results.

In a study of 144 adults, the aroma of rosemary essential oil improved overall quality of memory compared with no aroma, but slowed speed of memory ^{4Reference 4Moss et al. · 2003RCTAromas of rosemary and lavender essential oils differentially affect cognition and mood in healthy adults — randomisedView study →}.

In 80 healthy adults, a single 250 mL drink of rosemary water produced small improvements in cognition, along with changes in blood oxygen use in the brain ^{5Reference 5Moss et al. · 2018RCTAcute ingestion of rosemary water: Evidence of cognitive and cerebrovascular effects in healthy adults — randomised controlled trialView study →}.

In 28 older adults, dried leaf powder had a two-way dose effect: 750 mg improved speed of memory, while 6,000 mg impaired it ^{6Reference 6Pengelly et al. · 2012RCTShort-term study on the effects of rosemary on cognitive function in an elderly population — randomised controlled trialView study →}.

In 68 university students, 500 mg of rosemary twice daily for a month improved self-rated memory compared with placebo ^{8Reference 8Nematolahi et al. · 2018RCTEffects of Rosmarinus officinalis L. on memory performance, anxiety, depression, and sleep quality in university students: a randomized clinical trialView study →}.

A two-week pilot trial in 44 adults of a combined sage, rosemary and melissa extract found no overall effect on word recall, though adults under 63 improved ^{7Reference 7Perry et al. · 2018RCTA randomised double-blind placebo-controlled pilot trial of a combined extract of sage, rosemary and melissa on memory in healthy subjects — RCTView study →}. A meta-analysis of animal studies found a consistent improvement in memory in laboratory animals, with wide differences between studies ^{9Reference 9Hussain et al. · 2022Meta-analysisCognition enhancing effect of rosemary (Rosmarinus officinalis L.) in lab animal studies: a systematic review and meta-analysisView study →}.

Gap: trials are small, short, and heterogeneous in preparation (aroma vs water vs powder); no adequately powered trial of a defined oral dose over months.

Rosemary essential oil and its diterpenes show broad antimicrobial activity in the laboratory. Carnosic acid and carnosol block Staphylococcus aureus quorum sensing, the agr system that switches on its virulence, at concentrations as low as 5 μM, including in strains taken from people with atopic dermatitis ^{18Reference 18Nakagawa et al. · 2020In vitroRosmarinus officinalis L. (Rosemary) Extracts Containing Carnosic Acid and Carnosol are Potent Quorum Sensing Inhibitors of Staphylococcus aureus Virulence — in vitroView study →}.

In one set of six rosemary oils, antifungal activity was weak: they did not inhibit Candida albicans or Aspergillus niger at the concentrations tested, though most inhibited Cryptococcus neoformans ^{1Reference 1Satyal et al. · 2017In vitroChemotypic Characterization and Biological Activity of Rosmarinus officinalis — in vitroView study →}.

All of this is laboratory work. There are no human infection trials, and the concentrations active in vitro are unlikely to be reached by ordinary oral use.

Carnosic acid protects neurons in models of stroke and neurodegeneration, by activating Nrf2, preserving mitochondrial function and damping inflammation in the brain ^{20,22Reference 20Mirza et al. · 2023ReviewNeuroprotective Effects of Carnosic Acid: Insight into Its Mechanisms of Action — reviewView study →Reference 22Ghasemzadeh Rahbardar et al. · 2020ReviewTherapeutic effects of rosemary (Rosmarinus officinalis L.) and its active constituents on nervous system disorders — reviewView study →}.

It can cross the blood-brain barrier and becomes active under oxidative stress, which has drawn interest in Alzheimer’s and Parkinson’s disease ^{20Reference 20Mirza et al. · 2023ReviewNeuroprotective Effects of Carnosic Acid: Insight into Its Mechanisms of Action — reviewView study →}.

All of the evidence is preclinical. No human trial of rosemary or carnosic acid has been run in a neurodegenerative disease.

In mice, carnosic acid reduced fat build-up and inflammation in alcohol-related liver injury, by inhibiting the P2X7R–NLRP3 inflammasome and the formation of neutrophil extracellular traps ^{14Reference 14Zuo et al. · 2023AnimalCarnosic acid suppressed the formation of NETs in alcoholic hepatosteatosis based on the P2X7R-NLRP3 axis — mouseView study →}. A carnosic-acid-rich rosemary extract fed for 16 weeks reduced liver fat in mice on a high-fat diet ^{15Reference 15Zhao et al. · 2015AnimalCarnosic acid as a major bioactive component in rosemary extract ameliorates high-fat-diet-induced obesity and metabolic syndrome — mouseView study →}.

⚠ The one direct human test was null. In an 8-week randomised trial in 110 people with non-alcoholic fatty liver disease, 4 g a day of rosemary leaf powder was added to a weight-loss diet. Liver enzymes and metabolic markers improved in both groups, with no difference between rosemary and placebo apart from one marker of insulin-producing cell function ^{16Reference 16Akbari et al. · 2022RCTEffect of rosemary leaf powder with weight loss diet on lipid profile, glycemic status, and liver enzymes in patients with nonalcoholic fatty liver disease — randomized controlled trialView study →}.

Gap: the strongest human trial to date was negative; benefit is confined to animal models and specific extracts.

A 2011 review of animal and cell studies found that rosemary extract, carnosol, carnosic acid, ursolic acid and rosmarinic acid suppressed tumour development in the colon, breast, liver and stomach, and in melanoma and leukaemia cells. The effects were dose-related and acted at several stages of cancer development ^{19Reference 19Ngo et al. · 2011ReviewRosemary and cancer prevention: preclinical perspectives — reviewView study →}.

The proposed mechanisms overlap with the herb’s antioxidant and anti-inflammatory activity. There are no human cancer trials.

In a post-hoc analysis of a 4-week trial in working-age Japanese men, rosemary extract improved mood-disturbance and vigour scores in the men with the poorest mood at the start (8 on rosemary, 13 controls) ^{11Reference 11Araki et al. · 2020RCTEffects of Continuous Intake of Rosemary Extracts on Mental Health in Working Generation Healthy Japanese Men — randomized controlled trial (post-hoc)View study →}. In the student trial, 500 mg of rosemary twice daily for a month lowered anxiety and depression scores compared with placebo ^{8Reference 8Nematolahi et al. · 2018RCTEffects of Rosmarinus officinalis L. on memory performance, anxiety, depression, and sleep quality in university students: a randomized clinical trialView study →}.

⚠ In 73 young adults given an anxiety-provoking task, those exposed to rosemary scent scored higher for tension-anxiety and confusion than those given lavender or water ^{10Reference 10Burnett et al. · 2004Clinical trialScent and mood state following an anxiety-provoking task — clinical trialView study →}. Results depend on the route (an extract taken by mouth or an oil inhaled) and on the setting.

Gap: directly conflicting results across small trials; aroma may increase rather than decrease acute tension.

Rosemary leaf is a traditional remedy for wind, indigestion and cramping of the gut, and the European Medicines Agency recognises this as a traditional use ^{28Reference 28European Medicines Agency · 2024ReviewEuropean Union herbal monograph on Rosmarinus officinalis L., folium — Final, Revision 1 (EMA/HMPC/513940/2021) — regulatory monograph. https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-rosmarinus-officinalis-l-folium-revision-1_en.pdfView study →}. The volatile oil relaxes gut smooth muscle, in line with the antispasmodic activity described for the essential oil and its monoterpenes ^{22Reference 22Ghasemzadeh Rahbardar et al. · 2020ReviewTherapeutic effects of rosemary (Rosmarinus officinalis L.) and its active constituents on nervous system disorders — reviewView study →}.

There are no controlled human trials of rosemary for indigestion or gut spasm.

In cultured rat muscle cells, carnosic acid at 2 μmol/L doubled glucose uptake, a response similar to insulin and metformin. It worked through AMPK, the cell’s energy sensor, and did not increase the amount of the GLUT4 or GLUT1 glucose transporters at the cell surface ^{17Reference 17Naimi et al. · 2017In vitroCarnosic acid as a component of rosemary extract stimulates skeletal muscle cell glucose uptake via AMPK activation — in vitroView study →}. In mice on a high-fat diet for 16 weeks, carnosic-acid-rich rosemary extract reduced weight gain, blood glucose and insulin, and liver fat ^{15Reference 15Zhao et al. · 2015AnimalCarnosic acid as a major bioactive component in rosemary extract ameliorates high-fat-diet-induced obesity and metabolic syndrome — mouseView study →}.

The one human trial to measure blood sugar was the 8-week fatty liver trial of 4 g a day of rosemary leaf powder. Fasting glucose, insulin and insulin resistance fell in both groups, with no difference between rosemary and placebo ^{16Reference 16Akbari et al. · 2022RCTEffect of rosemary leaf powder with weight loss diet on lipid profile, glycemic status, and liver enzymes in patients with nonalcoholic fatty liver disease — randomized controlled trialView study →}.

Gap: the mechanism is in vitro and rodent only; no human trial has shown a glucose or insulin effect, and the one that looked was null.

In adult mouse wound models, an ethanol-based rosemary extract sped up wound closure and reduced scarring. The effect was traced to carnosic acid activating the TRPA1 receptor on sensory nerves in the skin, and mice lacking that receptor did not benefit ^{21Reference 21Rapp et al. · 2025AnimalCarnosic acid in topical rosemary extract enhances skin repair via TRPA1 activation — mouseView study →}.

This is a single animal study. There are no human wound trials.

General tolerance. Culinary amounts of rosemary and standardised food-grade extracts are well tolerated. A 2025 review concluded that rosemary is generally safe to eat and to use on the skin. The main reactions reported in people are allergic contact dermatitis and occasional hypersensitivity ^{23Reference 23Ghasemzadeh Rahbardar et al. · 2025ReviewToxicity and safety of rosemary (Rosmarinus officinalis): a comprehensive review — reviewView study →}.

Who should not take it. The European monograph lists hypersensitivity to rosemary as a contraindication and advises against the bath on broken or irritated skin. By mouth, it is not recommended with a blocked bile duct, cholangitis, liver disease or gallstones without medical supervision. It is not recommended for children under 12, for lack of data ^{28Reference 28European Medicines Agency · 2024ReviewEuropean Union herbal monograph on Rosmarinus officinalis L., folium — Final, Revision 1 (EMA/HMPC/513940/2021) — regulatory monograph. https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-rosmarinus-officinalis-l-folium-revision-1_en.pdfView study →}.

Baths. People with high blood pressure should take a full hot rosemary bath with caution ^{28Reference 28European Medicines Agency · 2024ReviewEuropean Union herbal monograph on Rosmarinus officinalis L., folium — Final, Revision 1 (EMA/HMPC/513940/2021) — regulatory monograph. https://www.ema.europa.eu/en/documents/herbal-monograph/final-european-union-herbal-monograph-rosmarinus-officinalis-l-folium-revision-1_en.pdfView study →}.

Essential oil. In laboratory and worm-model screens, rosemary oil was slightly more toxic than citrus or eucalyptus oils, and all three irritated mucous membranes at a 0.5% concentration ^{25Reference 25Lanzerstorfer et al. · 2021In vitroAcute, reproductive, and developmental toxicity of essential oils assessed with alternative in vitro and in vivo systems — in vitroView study →}.

High-dose animal studies. Animal studies at high doses report reduced sperm production, testosterone and sperm quality, and at very high doses liver and kidney changes ^{23Reference 23Ghasemzadeh Rahbardar et al. · 2025ReviewToxicity and safety of rosemary (Rosmarinus officinalis): a comprehensive review — reviewView study →}. A regulatory reproductive-toxicity study in rats found no general or reproductive toxicity from a food-grade acetone extract at up to 316–401 mg/kg a day ^{24Reference 24Phipps et al. · 2021AnimalReproductive and developmental toxicity screening study of an acetone extract of rosemary — animal modelView study →}.

Drug interactions. In human liver cells, carnosic acid from rosemary both inhibited CYP2C9 and CYP3A4 and induced CYP3A4 and CYP2B6 ^{31Reference 31Dickmann et al. · 2012In vitroIn vitro hepatotoxicity and cytochrome P450 induction and inhibition characteristics of carnosic acid, a dietary supplement with antiadipogenic properties — in vitroView study →}. Rosemary extract blocked the drug pump P-glycoprotein in breast-cancer cells ^{32Reference 32Plouzek et al. · 1999In vitroInhibition of P-glycoprotein activity and reversal of multidrug resistance in vitro by rosemary extract — in vitroView study →}.

In rats fed rosemary extracts for two weeks, liver UGT and other detoxifying enzymes rose ^{33Reference 33Debersac et al. · 2001AnimalInduction of cytochrome P450 and/or detoxication enzymes by various extracts of rosemary: description of specific patterns — animal modelView study →}. No human interaction study has been done.