Editing Achillea millefolium (section)

== Toxicity ==
{{see also|List of herbs with known adverse effects}}

Yarrow can cause [[Allergic contact dermatitis|allergic skin rashes]].<ref name="Haus">{{cite journal | last1=Hausbn | first1=B. M. | last2=Bheuer | first2=J. | last3=Weglewski | first3=J. | last4=Rucker | first4=G. | title=α-Peroxyachifolid and other new sensitizing sesquiterpene lactones from yarrow (''Achillea millefolium'' L., Compositae) | journal=Contact Dermatitis | volume=24 | issue=4 | year=1991 | issn=0105-1873 | pmid=1868717 | doi=10.1111/j.1600-0536.1991.tb01722.x | pages=274–280| s2cid=24643321 }}</ref> It reportedly can induce menstruation and cause miscarriages.<ref name=":3" />

According to the [[American Society for the Prevention of Cruelty to Animals]], yarrow is toxic to dogs, cats, and horses, causing increased urination, vomiting, diarrhea and dermatitis.<ref>{{cite web |title=Toxic and Non-Toxic Plants: Yarrow |url=http://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/yarrow |publisher=ASPCA}}</ref>
When consumed by cows, an unfavorable flavor is given to their milk.<ref>{{Cite book|last=Reiner|first=Ralph E.|title=Introducing the Flowering Beauty of Glacier National Park and the Majestic High Rockies|publisher=Glacier Park, Inc.|year=1969|pages=16}}</ref> In a standard [[rodent model]] for reproductive toxicity, aqueous extracts of yarrow produced a significant increase in the percentage of abnormal sperm.<ref>{{cite journal |vauthors=Dalsenter P, Cavalcanti A, Andrade A, Araújo S, Marques M |year=2004 |title=Reproductive evaluation of aqueous crude extract of Achillea millefolium L. (Asteraceae) in Wistar rats |journal=Reprod Toxicol |volume=18 |issue=6 |pages=819–23 |doi=10.1016/j.reprotox.2004.04.011 |pmid=15279880|bibcode=2004RepTx..18..819D }}</ref>