Yarrow (Achillea millefolium) is a perennial flowering plant in the Asteraceae family, that is native to temperate regions in Asia, Europe and North America. It was introduced as a food for livestock in Australia and New Zealand, where it has become a common weed and spread widely over a variety of habitats. It has a powerful sweet scent, similar to chrysanthemums. In the garden, yarrow is a food source for many insects, and various birds such as starlings use it to line their nests, possibly to inhibit parasites. It is considered particularly useful as a companion plant, attracting beneficial insects such as ladybirds, hoverflies and predatory wasps that use insect pests as food for their larvae, and repelling unwanted pests. It can be planted to reduce soil erosion and has deep roots, making it drought tolerant, and mineral-rich leaves.
Part of yarrow’s botanical name, its genus Achillea, refers to Achilles the warrior in Greek legends, as Achilles was reputed to use yarrow to treat the wounds of his warriors. The name millefolium (thousand-leaf) comes from the featherlike leaves that are minutely divided.
Yarrow has a fascinating history, being one of the oldest known botanicals used by humans worldwide — it is one of the six medicinal plants whose pollen was found in a Neanderthal grave at Shanidar in Iraq, dated to about 50,000 BCE.
Active ingredients
The yarrow plant contains isovaleric acid, salicylic acid, asparagine, sterols and flavonoids. The main flavonoids are myricetin, hesperidin, quercetin, luteolin, apigenin, hyperoside and kaempferol, along with phenolic acids such as gallic acid, benzoic acid, chlorogenic acid, vanillic acid, caffeic acid and ferulic and cinnamic acid. The aerial parts of the plant are used, but only the traditional white-flowered variety is medicinal. The essential oil of yarrow is dark blue and contains proazulenes including chamazulene. Azulene can be found in both yarrow and wormwood and was named in 1863.
Therapeutic actions
Gastrointestinal — Yarrow has long been used to treat a range of digestive problems including ulcers and irritable bowel syndrome as an antispasmodic, and relieving stomach pain, diarrhoea, bloating and constipation. The anti-inflammatory flavonoids play a significant role in these conditions. The leaves are also astringent and a mild laxative.
Rat studies showed that yarrow extract protected against stomach damage induced by alcohol and indomethacin and improved the healing rate of chronic gastric ulcers by regenerating the gastric mucosa, with little to no toxicity. Yarrow tea was also useful in relieving the symptoms of irritable bowel syndrome.
The anti-inflammatory effects of yarrow were shown to be effective in reducing liver inflammation, particularly in non-alcoholic liver disease. In the liver it reduced inflammation from both hepatitis and malaria.
Neurological — In animal studies yarrow tea showed significant effects in reducing the secretion of cortisol — the hormone that rises during stress — so has stress management benefits, alleviating the symptoms of both depression and anxiety.
Yarrow has shown significant promise in reducing the inflammation of the brain, thereby potentially reducing symptoms of multiple sclerosis, Alzheimer’s disease and Parkinson’s disease, all conditions with an inflammatory component that impacts on movement disorders and muscle tone.
Rat studies have shown that it’s antioxidant effects translate into anti-seizure activity, indicating a potential use for sufferers of epilepsy. The flavonoid luteolin has research demonstrating a significant improvement in memory and cognitive function in rats by improving blood supply to the brain.
Hypertension — In Mexico, yarrow is a traditional medicine used as a treatment for diabetes and hypertension. Rat studies were used to determine its effectiveness and an extract from the flowers showed a potent vasorelaxant effect, reducing both systolic and diastolic blood pressure through various mechanisms.
Immune system — In antitumour studies the flavonoids and the essential oil of yarrow was shown to be effective against leukaemia in mice and had significant cytostatic activity (or growth inhibition) against human cervical adrenocarcinoma.
Reproductive system — In traditional medicine, it was often used as a women’s remedy, as an emmenagogue, which stimulates menstrual flow, and to relieve menstrual pain. Research has shown that yarrow has measurable phytoestrogenic activity, mainly through apigenin, giving yarrow both a protective and a therapeutic role that helps balance female hormones.
Skin — The anti-inflammatory effects of yarrow are particularly useful in skin inflammation, reducing skin ageing and skin infections and increasing the moisture-holding capacity of the skin.
Yarrow as an ointment or cream (or a wash) is also particularly useful in wound healing (as used traditionally), increasing fibroblasts, the cells that regenerate healthy connective tissue.
A study in 140 women over two weeks showed that an ointment made with yarrow and St John’s wort sped up the healing of episiotomy sites, surgical incisions on the vaginal wall made to assist childbirth.
Yarrow can also be used as an insect repellent and as a component of anti-inflammatory cosmetics.
Taking yarrow
Yarrow can cause allergic skin rashes and if taken in too high doses may trigger menstruation and cause miscarriages. It is therefore contraindicated in pregnancy. It is also toxic to dogs, cats and horses, and cows that eat yarrow produce an unpleasant flavour in the milk.
References available on request.
