Medically reviewed by Drugs.com. Last updated on Oct 22, 2020.
Scientific Name(s): Rosmarinus officinalis L.
Common Name(s): Anthos, Old man, Rosemary
Clinical studies supporting traditional uses of rosemary are limited. A few small studies of questionable quality have suggested altered perception of pain and improved speed of recall with rosemary aromatherapy. Oral rosemary has been evaluated for potential use in dementia. Clinical studies, sometimes conducted by the product manufacturer, have used rosemary in combination with other ingredients (such as those found in commercial preparations), making it difficult to attribute efficacy to any one agent. Potential applications in alopecia and cancer, and as an antioxidant, have been studied.
Traditional uses include 2 g of chopped leaf infused in water, or 2 to 4 g of the shoot. Rosemary leaf is approved in the Complete German Commission E Monographs for dyspepsia, high blood pressure, and rheumatism at doses of 4 to 6 g/day, although evidence is lacking to support such indications. The essential oil has been used at doses of 0.1 to 1 mL. In a clinical study, low oral doses (750 mg) of dried rosemary leaf powder improved memory speed in elderly patients, while higher doses (6 g) impaired memory speed. Studies evaluating rosemary as aromatherapy used 3 to 4 drops for inhalation.
Contraindications have not yet been identified.
Generally recognized as safe (GRAS) when used as food. Avoid dosages above those found in food because safety and efficacy are unproven. Rosemary may have emmenagogue and abortifacient effects.
None well documented.
Dermatitis and allergy to rosemary have been reported. Although case reports of seizures due to rosemary are lacking, the potential for toxicity exists, possibly due to the ketone content of the plant.
Information is limited. As with most essential oils, ingestion of large amounts can be toxic. Antigonadotrophic activity has been described in mice, and an anti-implantation effect has also been described in rat experimentation.
- Lamiaceae (mint)
R. officinalis grows as a small evergreen shrub with thick, aromatic leaves. The plant has small, pale blue flowers that bloom in late winter and early spring. Although rosemary is native to the Mediterranean, it is now cultivated worldwide, with more than 20 varieties described. R. officinalis should not be confused with bog rosemary (Andromeda polifolia) or marsh rosemary (Rhododendron tomentosum) from the heath family.1, 2, 3, 4
Rosemary is a widely used culinary spice. Rosemary has sometimes been traditionally said to grow only in gardens of households where the "mistress" is truly the "master."5 The plant has been used in traditional medicine for its astringent, tonic, carminative, antispasmodic, and diaphoretic properties. Extracts and the volatile oil have been used to promote menstrual flow and as abortifacients.5 Rosemary extracts are commonly found in cosmetics, and a lotion of the plant has been said to stimulate hair growth and prevent baldness.3 Historical reports regarding the therapeutic use of rosemary as a medicinal plant are available.6, 7 Rosemary, one of the oldest known medicinal herbs, was used centuries ago to enhance mental function and memory.3
Rosemary has a wide variety of volatile and aromatic components. The plant’s leaves contain 0.5% to 2.5% of volatile oil, with major components including monoterpene hydrocarbons (alpha- and beta-pinene), camphene, limonene, camphor (10% to 20%), borneol, cineole, linalool, and verbinol. Flavonoids in the plant include diosmetin, diosmin, genkwanin, luteolin, hispidulin, and apigenin.2, 8 Other terpenoid constituents in rosemary include triterpenes oleanolic and ursolic acids and diterpene carnosol.8 Phenols in rosemary include caffeic, chlorogenic, labiatic, neochlorogenic, rosmarinic, and salicylic acids.4, 8, 9
Uses and Pharmacology
Clinical studies, sometimes conducted by the product manufacturer, have used rosemary in combination with other ingredients (such as those found in commercial preparations), making it difficult to attribute efficacy to any one agent.
Rosemary oil has significant in vitro antibacterial, antifungal, and antiviral properties.4, 8, 9 Carnosic acid, isolated from rosemary, exhibited strong in vitro inhibitory effects against HIV protease in one study.10 Combination formulations that include rosemary oil have been used to treat sheep ringworm11 and as alternatives to growth-promoting antibiotics in chickens.12
Clinical data regarding the use of rosemary oil or extracts for antibacterial or antifungal use is limited. A report on the use of rosemary to treat head lice found it to be ineffective, although it has been traditionally used for this purpose.13
Although there is no clinical data regarding antioxidant use of rosemary oil or extracts, antioxidant activity may be the underlying mechanism of action for other pharmacological effects.
In vitro and animal studies have demonstrated anticancer effects of rosemary extracts (especially carnosol and carnosic, ursolic, and rosemarinic acids), with a variety of mechanisms of action proposed, including induction of apoptosis, radical scavenging, and inhibition of tumorigenesis.15
Dietary supplementation in laboratory animals with rosemary extract 1% resulted in a 47% decrease in the incidence of experimentally induced mammary tumors compared with results in controls.16, 17 This extract enhanced activities of enzymes that detoxify reactive substances in mouse liver and stomach.18 Skin tumors in mice were inhibited by application of rosemary extract to the area.19
Although in vitro studies have assessed use of rosemary extract on human cancer tissues, including human ovarian cancer cells,20 there is no clinical data regarding the use of rosemary in cancer, except as adjuvant therapy.15
A neuroprotective effect was demonstrated in vitro, and rosemary extract enhanced the synthesis of nerve growth factor in T98G human glioblastoma cells.9 In older studies using rodents, administration or inhalation of the oil affected the cerebral cortex, decreased immobility duration (antidepressant-like effects), and improved endurance tests.9
Studies have examined the aromatherapeutic effects of rosemary oil, with improved recall demonstrated in at least 2 small, randomized controlled trials.21, 22 Although experimental studies showed decreased anxiety and increased alertness with rosemary oil inhalation, additional studies are needed.9 One study demonstrated improved speed but not accuracy in computing mathematical calculations.9, 23 Rosemary aromatherapy improved dementia scores in another study. Two studies have suggested that the effects of rosemary essential oil in managing pain may have been due to altered perceptions rather than direct analgesia.25, 26
Clinical studies evaluating the administration of oral rosemary extracts demonstrated equivocal results, with one study suggesting a dose-dependent effect.27, 28 In a crossover study of 28 elderly participants, low-dose rosemary (750 mg) improved measures of memory speed, whereas higher doses (6 g) impaired responses.27 A study of healthy young adults found no effect on motivation to perform cognitive tasks with administration of rosemary 1.7 g orally with olfactory senses blocked.28
A study in mice demonstrated that rosemary leaf extract applied topically improved hair growth, possibly via inhibition of testosterone reductase.29
In a randomized clinical trial evaluating rosemary oil and minoxidil 2% in androgenetic alopecia (N = 100), no change in outcome measures at 3 months occurred; however, at 6 months both groups showed increased hair counts on photographic assessment from baseline. Effects of rosemary oil were reported to be equivalent to those of minoxidil.30 Although older studies suggested increased circulation in the scalp due to rosemary extracts, because combination therapies were used it is difficult to attribute efficacy to a particular agent.9 Other dermatological studies, in dermatitis and ultraviolet radiation, have also used combination preparations.9, 31, 32
Antispasmodic action of rosemary oil in isolated guinea pig smooth muscle and cardiac tissue has been described, although the isolated spasmogenic constituent pinene is inactive on cardiac muscle.3
Limited laboratory studies have suggested a hypoglycemic effect.9 A clinical study evaluating rosemary in combination with polyunsaturated fatty acids in children with type 1 diabetes as a strategy to improve the oxidative damage had equivocal results.33
Traditional uses include 2 g of chopped leaf infused in water, or 2 to 4 g of the shoot. Other decoctions have been described.3 Rosemary leaf is approved in the Complete German Commission E Monographs for dyspepsia, high blood pressure, and rheumatism at doses of 4 to 6 g/day, although evidence is lacking to support such indications. The essential oil has been used at doses of 0.1 to 1 mL.34
In a clinical study, low oral doses (750 mg) of dried rosemary leaf powder improved memory speed in elderly patients, while higher doses (6 g) impaired memory speed.27
Pregnancy / Lactation
GRAS when used as food. Avoid dosages above those found in food because safety and efficacy are unproven. Rosemary inhibited uterotropic actions of estradiol and estrone in rodent studies.35 Rosemary may have emmenagogue and abortifacient effects, although evidence is weak.3, 36
Case reports are lacking, but rosemary may interact with medicines affected by the cytochrome P450 system.9
Dermatitis and allergy to rosemary have been reported.2, 3 Although case reports of seizures due to rosemary are lacking, the potential for toxicity exists, possibly due to camphor and other monoterpene ketone content of the plant.37
Information is limited. As with most essential oils, ingestion of large amounts can be toxic.3 Antigonadotrophic activity has been described in mice38 and an anti-implantation effect has also been described in rat experimentation.39
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