Traditional cultures spanning the Americas, Europe, and Asia have reported using yarrow to treat conditions or distress of the gastrointestinal system, menstruation, skin, blood (diabetes, cholesterol, hypertension, infection, varicosity), respiratory system, and rheumatism.^[1]

Over 76 different Indigenous peoples of the Americas (notably the Paiute, Thompson/Ntlakyapamuk, Iroquois, Shoshoni, and Cheyenne tribes) have used yarrow as a traditional treatment for over 50 different conditions and ailments. The most frequently cited uses for yarrow among First Nations are as a dermatological aid, analgesic, cold remedy, fever reducer, and antidiarrheal, and to aid in gynecological, gastrointestinal, or rheumatic conditions.^[2]

Yarrow has been explored most prominently as a treatment for wounds and general skin/membrane inflammation. More specifically, yarrow has been studied for: healing in oral mucositis produced as a side effect of chemotherapy,^[3][4] episiotomy,^[5] leishmaniasis lesions,^[6] vaginal irritations/infections,^[11][12] gingival inflammation,^[10] tonsillitis,^[9] nipple cracking during breastfeeding,^[7] and atopic dermatitis.^[8] In these studies, yarrow was most often applied topically, but whenever it’s applied to mucosal membranes (i.e., when applied orally or vaginally) it could potentially have systemic effects too.

Where wound healing is concerned (oral mucositis, episiotomy, nipple cracking, and leishmaniasis lesions), topical application of yarrow seems promising for healing oral mucositis (15 ml solution, 4x per day for 14 days), nipple cracking (30 g yarrow plus 1 liter water breast wash, twice per day for 7 days), and vaginal episiotomy (5% ointment in 30g tube, applied 2x per day for 10 days), but was ineffective for lesions caused by leishmaniasis infection.^{[3][4][5][6][7]}

In instances of skin or oral/vaginal membrane inflammation and infections, yarrow is frequently combined with other herbs, such as calendula, St. John’s wort, juniper, nettle, marshmallow root, chamomile, and panax ginseng.^{[8][9][10][11]} In studies using yarrow plus mixed herbs for a variety of conditions (vaginitis, gingivitis, tonsillitis, and atopic dermatitis), only one trial concluded that yarrow combination therapy was more effective than the control/standard-of-care comparator (acute tonsillitis; proprietary combination extract BNO1030; 4 drops administered orally, 3-4x per day for 10 days).^[9] When yarrow ointment was compared to a standard-of-care ointment (5 g ointment applied directly to site, nightly, for 7 days), standard of care was found to be superior to yarrow in reducing the signs and symptoms of vulvovaginal candidiasis.^[12]

Though yarrow has a tradition of use for menstrual and reproductive concerns, there aren’t many clinical studies on the subject. The most promising clinical evidence found that the use of yarrow tea (4 g dried flowers) may help reduce the pain associated with dysmenorrhea (painful menstruation) when taken three times a day during the first three days of the monthly cycle.^[14] Preclinical evidence from rat trials may also support the idea that other achilleas (not A. millefolium , but A. biebersteinii and A. cretica) could aid in management of endometriosis symptoms, but these conclusions should not be applied directly to humans without further clinical support.^[18][19]

There is some evidence that yarrow may be useful for ameliorating vaginal and breast infections, irritations, and wounds. See the FAQs on wound healing and skin/mucosal irritations for further details on these studies.

A study that included yarrow as a component of a multi-herb capsule (in combination with Boswellia and ginger) for irritable bowel syndrome found that, when this combination was taken once every 8 hours over a month, male participants saw statistically significant improvements in quality-of-life scores; however, overall reductions in average symptom severity, anxiety, and depression scores were not strong enough to recommend yarrow for this condition.^[13] Beyond this, only preclinical evidence exists to suggest that achilleas (A. Millefolium and A. nobilis) administered to rats could aid in reducing both peptic ulcers^[20] and stomach cramping.^[21][22] Again, clinical studies are needed before these results may be translated to human use.

Clinical trials have considered yarrow as a potential therapy (used both topically and systemically, as well as alone or in combination with other treatments) for chronic kidney disease,^[23] cirrhosis,^[24] chemotherapy-related fatigue,^[25][26] and multiple sclerosis.^[27]

When used alone, those with chronic kidney disease taking 1.5 g of powdered yarrow flower (3 days a week over 2 months) saw a marginal reduction in plasma nitrite and nitrates, while those taking a placebo saw increases in the same biomarkers.^[23] Liver compresses containing yarrow are sometimes used in integrative medicine; however, metastatic cancer patients undergoing chemotherapy saw no substantive reductions of self-reported fatigue and psychological distress when liver compresses containing yarrow were applied externally over the liver,^[26] and heart rate variability analysis in a subset of participants were not conclusive.^[25].

As a combination therapy, yarrow seems to be somewhat more successful. A six-month study of people with cirrhosis found that those taking a multi-ingredient (Tamarix gallica 16 mg, iron-based ayurvedic preparation Mandur Bhasma 33 mg, and extracts of Capparis spinosa 65 mg, Cichorium intybus 65 mg, Solanum nigrum 32 mg, Cassia occidentalis 16 mg, Terminalia arjuna 32 mg, and Achillea millefolium 16 mg) tablet three times daily saw reductions in serum ALT and AST (biomarkers of liver damage), and abdominal swelling, compared to placebo.^[24] Similarly, when a yarrow extract containing 0.28 mg/g of luteolin and 1.58 mg/g of apigenin was studied as an add-on therapy for multiple sclerosis, the groups taking 250 or 500 mg/d of the yarrow extract for one year saw reductions in multiple sclerosis relapse rates, volume of lesions, and improved cognitive performance scores compared to placebo.^[27]