Yarrow

The drug is the flowering aerial part. Western herbalism classes yarrow above all as a styptic and vulnerary, which Culpeper describes as “drying and binding” ^{36Reference 36Battaglia S · 2003The Complete Guide to Aromatherapy (2nd ed.)}. Grieve gives its actions as diaphoretic, astringent, tonic, stimulant and mildly aromatic ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}.

Most of its traditional indications concern bleeding and broken tissue: open wounds, nosebleeds and bleeding piles. Scottish Highlanders made an ointment of the fresh herb for wounds and piles, and Linnaeus recommended the bruised fresh herb as a wound herb and styptic ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}.

Taken internally as a warm infusion, yarrow tea was a remedy for severe colds and the beginning of fevers, to open the pores and bring on a sweat ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}. A decoction of the whole plant was given for kidney disorders, and the same decoction was used as a hair wash against baldness ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}.

Other folk uses include the fresh leaves chewed for toothache, a rolled leaf put in the nostril to relieve headache, and yarrow tea drunk in Orkney against melancholy ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}. In the seventeenth century the leaves went into salads ^{35Reference 35A Modern Herbal (Grieve M) · 1931YarrowView study →}.

In modern German practice, Commission E approves yarrow internally for loss of appetite and dyspeptic complaints, including cramping discomfort, and externally as a sitz bath or compress for skin inflammation and slow-healing wounds ^{33Reference 33Németh E · 2008ReviewBiological activities of yarrow species (Achillea spp.) — [review]View study →}.

Native Americans used yarrow to treat earaches, diarrhoea and bleeding ^{39Reference 39Trock · 2006AchilleaView study →}.

In Mexican traditional medicine yarrow is used for high blood pressure and diabetes ^{21Reference 21Arias-Durán L et al. · 2021AnimalAntihypertensive and vasorelaxant effect of leucodin and achillin isolated from Achillea millefolium through calcium channel blockade and NO production: in vivo, functional ex vivo and in silico studies — [rat in vivo]View study →}. In Brazilian folk medicine, where it is called mil folhas, it is taken for digestive complaints, inflammation, pain, wounds and bleeding, and for anxiety and insomnia ^{22,24Reference 22Cavalcanti AM et al. · 2006AnimalSafety and antiulcer efficacy studies of Achillea millefolium L. after chronic treatment in Wistar rats — [rat in vivo]View study →Reference 24Baretta IP et al. · 2012AnimalAnxiolytic-like effects of acute and chronic treatment with Achillea millefolium L. extract — [mouse in vivo]View study →}.

Yarrow is described as cooling and drying, a herb that stimulates the liver and regulates the flow of Qi ^{36Reference 36Battaglia S · 2003The Complete Guide to Aromatherapy (2nd ed.)}.

It is given for inflammatory and digestive complaints and for stagnant Qi ^{36Reference 36Battaglia S · 2003The Complete Guide to Aromatherapy (2nd ed.)}.

Yarrow’s best-replicated activity is relaxation of smooth muscle. A crude aqueous-methanol extract relaxed spontaneous and K⁺-induced contractions in rabbit jejunum and shifted calcium curves rightward, as verapamil does ^{8Reference 8Yaeesh S et al. · 2006AnimalStudies on hepatoprotective, antispasmodic and calcium antagonist activities of the aqueous-methanol extract of Achillea millefolium — [mouse in vivo]View study →}.

A hydroalcoholic extract relaxed acetylcholine- and KCl-induced contractions in rat ileum, unblocked by propranolol or L-NAME, pointing to calcium-channel blockade ^{9Reference 9Moradi MT et al. · 2013AnimalAntispasmodic effects of yarrow (Achillea millefolium L.) extract in the isolated ileum of rat — [rat in vivo]View study →}.

In guinea-pig trachea it acted partly through muscarinic inhibition ^{10Reference 10Feizpour A et al. · 2013In vitroThe effect of hydro-ethanolic extract of Achillea millefolium on muscarinic receptors of guinea pig tracheal smooth muscle — [in vitro]View study →}.

The flavonoid fraction carries much of the activity ^{32Reference 32Benedek B · 2007ReviewAchillea millefolium L. s.l. revisited: recent findings confirm the traditional use — [review]View study →}.

No human trial of yarrow for spasm or colic exists.

Gap: No human data; the effective doses relaxed isolated tissue at concentrations not clearly reached by drinking the herb.

Yarrow’s main traditional use is as a styptic and wound herb, and it has the herb’s clearest human evidence. In a double-blind trial of 140 first-time mothers, a yarrow ointment reduced episiotomy pain, redness, oedema and bruising compared with placebo ointment and no treatment, without changing discharge or wound breakdown ^{3Reference 3Hajhashemi M et al. · 2018RCTThe effect of Achillea millefolium and Hypericum perforatum ointments on episiotomy wound healing in primiparous women — [double-blind randomised]View study →}.

In 56 chemotherapy patients with oral mucositis, a mouthwash of yarrow distillate added to the routine rinse reduced the severity of mouth sores over 14 days, while sores worsened with the routine rinse alone ^{4Reference 4Miranzadeh S et al. · 2015RCTEffect of adding the herb Achillea millefolium on mouthwash on chemotherapy induced oral mucositis in cancer patients: a double-blind randomized controlled trial — [double-blind randomised]View study →}.

A placebo-controlled cosmetic trial found a 2% extract improved the appearance of wrinkles and pores over two months, and the extract improved epidermal differentiation markers in cultured human skin ^{6Reference 6Pain S et al. · 2011RCTSurface rejuvenating effect of Achillea millefolium extract — [randomised placebo-controlled]View study →}.

Laboratory wound-healing work in the genus has mostly used other Achillea species, such as A. kotschyi ^{12Reference 12Agar OT et al. · 2015In vitroComparative studies on phenolic composition, antioxidant, wound healing and cytotoxic activities of selected Achillea L. species growing in Turkey — [in vitro]View study →}.

Gap: Only one A. millefolium skin-wound RCT, and it tested an ointment; the classic styptic (“stop bleeding”) claim itself has not been tested in a controlled human setting.

Yarrow is a consistent radical scavenger in vitro. Its essential oil reduced the DPPH radical (IC₅₀ ≈ 1.6 µg/mL), scavenged hydroxyl radicals and inhibited lipid peroxidation ^{11Reference 11Candan F et al. · 2003In vitroAntioxidant and antimicrobial activity of the essential oil and methanol extracts of Achillea millefolium subsp. millefolium Afan. — [in vitro]View study →}.

In the methanolic extract, the antioxidant activity tracks chlorogenic acid and its derivatives and the flavonol glycosides ^{14Reference 14Vitalini S et al. · 2011In vitroPhenolic compounds from Achillea millefolium L. and their bioactivity — [in vitro]View study →}.

The sesquiterpene lactone achillolide A reduced reactive oxygen species and blocked MAPK activation in cultured astrocytes under oxidative stress ^{13Reference 13Elmann A et al. · 2016In vitroAchillolide A protects astrocytes against oxidative stress by reducing intracellular reactive oxygen species and interfering with cell signaling — [in vitro]View study →}.

All of it is in vitro and cell-based, with no evidence that oral yarrow raises antioxidant capacity or lowers oxidative markers in a person.

Newly described guaianolides from A. millefolium (millefolactons) inhibited 15-lipoxygenase. Millefolacton C also suppressed nitric-oxide release, TNF-α, IL-6, IL-18, PGE₂, iNOS, COX-2 and the NLRP3 inflammasome in LPS-stimulated microglial cells ^{15Reference 15Li H et al. · 2023In vitroGuaianolides from Achillea millefolium L. and their anti-inflammatory activity — [in vitro]View study →}.

Yarrow extract and its flavonoid fraction inhibited human neutrophil elastase (IC₅₀ ≈ 20 µg/mL), a protease central to inflammation, giving a second distinct mechanism ^{16Reference 16Benedek B et al. · 2007In vitroAchillea millefolium L. s.l. — is the anti-inflammatory activity mediated by protease inhibition? — [in vitro]View study →}.

A hydroalcoholic extract at 500 mg/kg reduced writhing in mice by 65%, but had no effect in the hot-plate or formalin pain tests ^{26Reference 26Pires JM et al. · 2009AnimalAntinociceptive peripheral effect of Achillea millefolium L. and Artemisia vulgaris L. — [mouse in vivo]View study →}.

No human anti-inflammatory trial exists: the cytokine and enzyme effects come from isolated cells and rodent tissue at defined concentrations.

In mice given D-galactosamine plus lipopolysaccharide, pre-treatment with crude extract at 300 mg/kg cut mortality from 100% to 40%, and at 150–600 mg/kg it blunted the rise in ALT and AST, with histology confirming preserved liver architecture ^{8Reference 8Yaeesh S et al. · 2006AnimalStudies on hepatoprotective, antispasmodic and calcium antagonist activities of the aqueous-methanol extract of Achillea millefolium — [mouse in vivo]View study →}.

In streptozotocin-diabetic rats a hydroalcoholic extract lowered liver enzymes alongside glucose and lipids, comparably to metformin on several markers ^{17Reference 17Rezaei S et al. · 2020AnimalHydroalcoholic extract of Achillea millefolium improved blood glucose, liver enzymes and lipid profile compared to metformin in streptozotocin-induced diabetic rats — [rat in vivo]View study →}.

A fraction rich in dicaffeoylquinic acids increased bile flow in the isolated rat liver by up to 47% ^{23Reference 23Benedek B et al. · 2006AnimalCholeretic effects of yarrow (Achillea millefolium s.l.) in the isolated perfused rat liver — [rat in vivo]View study →}.

No human hepatoprotective trial exists, the doses are high relative to ordinary intake, and the models are acute chemical injury rather than chronic liver disease.

Several rodent studies found a blood-pressure-lowering effect. Crude extract produced a dose-dependent fall in arterial pressure in anaesthetised rats, with negative inotropic effects on guinea-pig atria and verapamil-like relaxation of rabbit aortic rings ^{19Reference 19Khan AU · 2011AnimalBlood pressure lowering, cardiovascular inhibitory and bronchodilatory actions of Achillea millefolium — [rat in vivo]View study →}.

A hydroethanolic extract lowered mean arterial pressure in rats, and the isolated flavonoid artemetin reproduced it, partly through ACE inhibition ^{20Reference 20de Souza P et al. · 2011AnimalHypotensive mechanism of the extracts and artemetin isolated from Achillea millefolium L. in rats — [rat in vivo]View study →}.

The epimeric sesquiterpene lactones leucodin and achillin, given by mouth, lowered blood pressure in spontaneously hypertensive rats via calcium-channel blockade and nitric-oxide-mediated vasorelaxation ^{21Reference 21Arias-Durán L et al. · 2021AnimalAntihypertensive and vasorelaxant effect of leucodin and achillin isolated from Achillea millefolium through calcium channel blockade and NO production: in vivo, functional ex vivo and in silico studies — [rat in vivo]View study →}.

There is no human blood-pressure data, and the oral bioavailability of these compounds from the herb is unknown.

Yarrow has one positive human trial for menstrual pain. In a double-blind randomized study, female students with primary dysmenorrhea drank yarrow as a teabag preparation for three days across two cycles; the mean reduction in visual-analogue pain score was significantly greater than placebo at one and two months ^{2Reference 2Jenabi E · 2015RCTEffect of Achillea millefolium on relief of primary dysmenorrhea: a double-blind randomized clinical trial — [double-blind randomised]View study →}.

Yarrow’s antispasmodic (calcium-channel) ^{9Reference 9Moradi MT et al. · 2013AnimalAntispasmodic effects of yarrow (Achillea millefolium L.) extract in the isolated ileum of rat — [rat in vivo]View study →} and anti-inflammatory (prostaglandin/COX-2) ^{15Reference 15Li H et al. · 2023In vitroGuaianolides from Achillea millefolium L. and their anti-inflammatory activity — [in vitro]View study →} activities act on mechanisms involved in menstrual cramping. The trial was small, at a single centre, and had no objective endpoints.

Gap: One unreplicated trial; no measurement of prostaglandins or menstrual blood loss.

Antidiabetic activity is supported by rodent work only. A hydroalcoholic extract, injected into the abdomen of diabetic rats, lowered blood glucose, raised insulin and reduced pancreatic IL-1β and iNOS gene expression, which drive β-cell destruction ^{18Reference 18Zolghadri Y et al. · 2014AnimalAchillea millefolium L. hydro-alcoholic extract protects pancreatic cells by down regulating IL-1β and iNOS gene expression in diabetic rats — [rat in vivo]View study →}.

In streptozotocin-diabetic rats the extract given by mouth significantly lowered blood glucose, triglycerides and LDL-cholesterol while raising HDL, comparably to metformin on several endpoints ^{17Reference 17Rezaei S et al. · 2020AnimalHydroalcoholic extract of Achillea millefolium improved blood glucose, liver enzymes and lipid profile compared to metformin in streptozotocin-induced diabetic rats — [rat in vivo]View study →}.

A registered human trial of a multi-herb “antidiabetic tea” containing yarrow exists, but its design cannot isolate yarrow’s contribution.

No controlled human data exists for yarrow alone.

A hydroalcoholic extract produced diazepam-like anxiolytic behaviour in mice after single and 25-day dosing, without affecting movement ^{24Reference 24Baretta IP et al. · 2012AnimalAnxiolytic-like effects of acute and chronic treatment with Achillea millefolium L. extract — [mouse in vivo]View study →}. Flumazenil only partly blocked the effect, and the extract did not bind the benzodiazepine site, so the effect is probably not mediated through GABA-A receptors ^{24Reference 24Baretta IP et al. · 2012AnimalAnxiolytic-like effects of acute and chronic treatment with Achillea millefolium L. extract — [mouse in vivo]View study →}.

In a triple-blind add-on RCT in 75 people with multiple sclerosis, a year of aqueous extract (250 or 500 mg/day) reduced the annual relapse rate against placebo, and the 500 mg dose also reduced lesion volume ^{1Reference 1Ayoobi F et al. · 2019RCTAchillea millefolium is beneficial as an add-on therapy in patients with multiple sclerosis: a randomized placebo-controlled clinical trial — [randomised placebo-controlled]View study →}.

An aqueous extract also reduced oxidative stress, apoptosis and memory impairment in the hippocampus of morphine-treated rats ^{25Reference 25Mozafari N et al. · 2022AnimalNeuroprotective effect of Achillea millefolium aqueous extract against oxidative stress and apoptosis induced by chronic morphine in rat hippocampal CA1 neurons — [rat in vivo]View study →}.

Gap: The MS trial is single and small with broad secondary endpoints; the rest is rodent behavioral/biochemical data with no anxiety or cognition trial in people.

One rodent study supports gastroprotection. In Wistar rats the aqueous extract protected gastric mucosa against ethanol- and indomethacin-induced acute lesions and healed acetic-acid-induced chronic ulcers (ED₅₀ ≈ 32 mg/kg), while a 28–90-day safety arm found only slight changes in liver weight, cholesterol and glucose ^{22Reference 22Cavalcanti AM et al. · 2006AnimalSafety and antiulcer efficacy studies of Achillea millefolium L. after chronic treatment in Wistar rats — [rat in vivo]View study →}.

This is a single animal study, with no human gastric or dyspepsia trial behind it.

Antimicrobial activity is real in vitro but preparation-limited. The essential oil inhibited Streptococcus pneumoniae, Clostridium perfringens, Candida albicans and Mycobacterium smegmatis, while the water-insoluble parts of the methanolic extract had slight or no activity ^{11Reference 11Candan F et al. · 2003In vitroAntioxidant and antimicrobial activity of the essential oil and methanol extracts of Achillea millefolium subsp. millefolium Afan. — [in vitro]View study →}.

In a trial of 80 women, an aqueous-extract vaginal cream reduced vulvovaginal candidiasis symptoms but cleared Candida in fewer patients than clotrimazole (53% vs 77%) ^{5Reference 5Zakeri S et al. · 2020RCTThe effect of Achillea millefolium L. on vulvovaginal candidiasis compared with clotrimazole: a randomized controlled trial — [randomised controlled trial]View study →}.

The activity lives mainly in the oil, whose composition varies widely between samples, so an infusion or tincture does not reliably deliver it.

Gap: Efficacy is tied to the volatile oil at concentrations tea/tincture may not reach; the one human antifungal trial showed inferiority to standard treatment.

Tolerability. Rats given aqueous extract at 0.3–1.2 g/kg a day for 28 or 90 days showed only slight changes in liver weight, cholesterol and glucose, with no signs of relevant toxicity ^{22Reference 22Cavalcanti AM et al. · 2006AnimalSafety and antiulcer efficacy studies of Achillea millefolium L. after chronic treatment in Wistar rats — [rat in vivo]View study →}.

Allergy. Yarrow can cause allergic contact dermatitis. In patch testing, people sensitive to a Compositae mix containing yarrow also reacted to yarrow itself ^{30Reference 30Cosmetic Ingredient Review (Andersen FA · 2001ReviewFinal report on the safety assessment of Yarrow (Achillea millefolium) Extract — [review]View study →}. The reaction is linked to the sesquiterpene lactones ^{33Reference 33Németh E · 2008ReviewBiological activities of yarrow species (Achillea spp.) — [review]View study →}.

Quality. In a survey of 40 commercial samples, only half met European Pharmacopoeia standards ^{31Reference 31Benedek B et al. · 2008In vitroYarrow (Achillea millefolium L. s.l.): pharmaceutical quality of commercial samples — [in vitro]View study →}.

Blood pressure and sedatives. Yarrow extracts and constituents lower blood pressure in rats ^{19,20,21Reference 19Khan AU · 2011AnimalBlood pressure lowering, cardiovascular inhibitory and bronchodilatory actions of Achillea millefolium — [rat in vivo]View study →Reference 20de Souza P et al. · 2011AnimalHypotensive mechanism of the extracts and artemetin isolated from Achillea millefolium L. in rats — [rat in vivo]View study →Reference 21Arias-Durán L et al. · 2021AnimalAntihypertensive and vasorelaxant effect of leucodin and achillin isolated from Achillea millefolium through calcium channel blockade and NO production: in vivo, functional ex vivo and in silico studies — [rat in vivo]View study →} and have anxiolytic effects in mice ^{24Reference 24Baretta IP et al. · 2012AnimalAnxiolytic-like effects of acute and chronic treatment with Achillea millefolium L. extract — [mouse in vivo]View study →}. It may add to the effect of blood-pressure and sedative medicines, though this has not been studied in people. No human drug-interaction or CYP450 study has been done.

Sperm. At the highest dose tested, 1.2 g/kg a day for 90 days, a leaf extract increased the proportion of abnormal sperm in male rats ^{29Reference 29Dalsenter PR et al. · 2004AnimalReproductive evaluation of aqueous crude extract of Achillea millefolium L. (Asteraceae) in Wistar rats — [rat in vivo]View study →}.