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.[1] 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.[2][3]
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.