Benefits
Menstrual pain scores in a placebo-controlled tea trial
In a double-blind trial in 96 Iranian female university students with painful periods and no underlying cause, yarrow tea taken with each of three meals for 3 days in each of two cycles lowered pain scores more than a starch placebo after the first and second months. It used about 12 g of herb a day, two to six times the EU traditional guidance of 1 to 2 g taken 2 to 3 times daily, and has not been repeated.
Traditional use for appetite and mild cramping digestive complaints
EU regulators accept yarrow herb and flower teas and extracts as traditional herbal medicines for temporary loss of appetite and for mild cramping digestive complaints such as bloating and wind, based on long-standing use rather than trials. No controlled trial of yarrow alone has measured digestion in people; the only digestive trial found tested a three-herb blend.
Liver enzyme (ALT and AST) readings in a 90-day capsule trial
In 60 Iranian adults with type 2 diabetes, 500 mg/day of yarrow flower powder for 90 days lowered ALT and AST within the yarrow group but not the placebo group. Plain end-of-study comparisons between groups were not significant; an adjusted analysis was. Average enzyme levels were within the usual normal range, and the yarrow group started with higher AST.
Cholesterol and triglycerides in the same 90-day capsule trial
In the same trial, LDL cholesterol, total cholesterol and triglycerides fell within the yarrow group, while HDL did not change. End-of-study values did not differ significantly from placebo in a direct comparison; only an analysis adjusted for baseline values, age, sex and diabetes duration showed group differences. One small trial in people under medical care.
Add-on use in a one-year placebo-controlled neurology trial
In a triple-blind trial in 75 patients with multiple sclerosis, a yarrow water extract at 250 or 500 mg/day for one year, given as an add-on therapy, was reported to lower the yearly relapse rate and improve disability scores and some memory and attention tests versus placebo. One small trial in a diagnosed disease, not evidence for self-care.
Gut muscle activity in lab and animal studies
In guinea-pig intestine, yarrow's flavonoid fraction and its apigenin and luteolin relaxed contractions, mainly by blocking calcium entry. A standardized water extract instead contracted mouse and human stomach muscle strips through its choline and sped stomach emptying in mice. These lab and animal findings point in different directions and have not been tested in people taking yarrow.
Mechanism of action
Flavonoids relax intestinal muscle in lab tests
On isolated guinea-pig intestine, the flavonoids quercetin, luteolin and apigenin had the strongest antispasmodic activity, acting mainly by blocking calcium entry into muscle cells; rutin had no significant effect. The authors estimated that yarrow tea holds enough flavonoid to act in the gut, but this was not measured in people.
Choline stimulates stomach muscle in tissue studies
A standardized dry water extract of the flowering tops contracted mouse and human stomach muscle strips, an effect strongly reduced by atropine and reproduced by choline but not by rutin or apigenin, and it sped stomach emptying in mice. This is the proposed basis for the traditional appetite and indigestion use; it is tissue and animal work.
Sesquiterpene lactones drive skin allergy
Yarrow contains several sesquiterpene lactones of peroxide type; the main one, alpha-peroxyachifolid, was a strong sensitizer in guinea pigs. More than half of patients already sensitized to daisy-family plants reacted to a yarrow extract on patch testing, and EU monographs contraindicate yarrow in people with Asteraceae allergy.
Composition varies with plant type and product
Yarrow is a group of related plants whose essential oil differs with chromosome number: only some types make proazulenes such as chamazulene, and alpha-thujone ranged from none to over 26% of the oil across European samples. In 40 commercial herb samples only half met European Pharmacopoeia quality standards.
Clinical trials
Double-blind, randomized, placebo-controlled trial at a university in western Iran (July to November 2013). Teabags of 4 g yarrow flower powder or starch placebo, one cup in 300 ml hot water with each of three meals for 3 days, in 2 menstrual cycles; pain rated on a visual analog scale. (Jenabi et al. 2015, J Pediatr Adolesc Gynecol)
96 female university students with primary dysmenorrhea (number from the EU assessment addendum; the abstract does not state it).
The mean drop in pain score was larger with yarrow than placebo at 1 month (P = 0.001) and 2 months (P < 0.0001); the abstract gives no effect sizes. EU assessors noted that this dosing (about 12 g of herb a day) is significantly higher than the monograph posology, that the groups were small and limited to young unmarried students, and that no side effects were reported.
Double-blind, placebo-controlled trial at a diabetes clinic in Rafsanjan, Iran; one 500 mg capsule of ground dried yarrow flowers, or cellulose placebo, daily for 90 days; registered IRCT20230612058459N1. (Daneshvar-Ghahfarokhi et al. 2025, BMC Nutr)
70 adults aged 40 or older with type 2 diabetes enrolled; 60 analyzed (30 per group) after 5 per group were excluded.
ALT, AST, LDL, total cholesterol and triglycerides fell within the yarrow group but not within the placebo group; HDL did not change. Direct end-of-study comparisons between groups were not significant for any of these. An analysis adjusted for baseline values, age, sex and diabetes duration found group differences for all but HDL. AST was higher at baseline in the yarrow group (P = 0.037). No side effects were reported.
Triple-blind, randomized, placebo-controlled parallel-group trial by researchers in Rafsanjan, Iran; aqueous yarrow extract at 250 or 500 mg/day, or placebo, for 1 year as an add-on therapy. Primary outcome: annualized relapse rate. (Ayoobi et al. 2019, Phytomedicine)
75 patients with multiple sclerosis randomized to three groups.
Both doses lowered the annual relapse rate, and 500 mg/day reduced the mean change in MRI lesion volume. The authors also report a longer time to first relapse, better EDSS and MSFC scores, and better results on some memory and attention tests (word-pair learning, PASAT, WCST). A single small trial in a diagnosed disease; the abstract gives no effect sizes and it has not been repeated.
Randomized, placebo-controlled preliminary study; 1.5 g of powdered yarrow flower 3 days a week for 2 months, given in capsules per the EU assessment addendum. (Vahid et al. 2012, Iran J Kidney Dis)
31 patients with chronic kidney disease (16 yarrow, 15 placebo).
Plasma nitrite (0.82 to 0.63 µmol/L) and nitrate (50.55 to 44.09 µmol/L) fell slightly with yarrow and rose slightly on placebo, but the changes were not statistically significant. EU assessors report that one woman developed a skin rash and was withdrawn. A lab marker in a small group, not a kidney outcome.
Randomized, placebo-controlled trial at a psychosomatic clinic in Isfahan, Iran (2015 to 2016); one capsule of a Boswellia carterii, Zingiber officinale and Achillea millefolium blend, or starch placebo, every 8 hours for 1 month, with follow-up to 3 months. The paper does not state the amount of each herb or whether it was blinded. (Kazemian et al. 2017, J Res Med Sci)
60 adults with mild to moderate irritable bowel syndrome (Rome III criteria); 6 on the blend and 4 on placebo stopped in the first month and 8 more were excluded for poor compliance, leaving 20 and 22 analyzed. The groups differed at baseline in age and sex.
Abdominal pain severity and frequency, bloating, and anxiety and depression scores fell on the blend, while the changes on placebo were not significant; the change in pain severity differed between groups (P = 0.001). Four people on the blend reported nausea, itching or diarrhea. Quality of life differed between groups in men (P = 0.01) but not in women. With three herbs in one capsule, yarrow's own contribution cannot be judged.