Achillea millefolium, commonly known as yarrow, is a perennial herb in the Asteraceae, or daisy, family, native to temperate and subarctic Eurasia and Greenland and widely naturalized elsewhere. It thrives in sunny meadows, fields, and roadsides with well-drained soil. Its flowering tops and leaves are used medicinally and have a distinctly bitter taste and aromatic, herbaceous scent. Traditionally, yarrow is valued for anti-inflammatory, antispasmodic, and carminative properties - actions that help calm inflammation, relax muscular spasms, and relieve digestive gas. Its notable constituents include the flavonoids apigenin and luteolin, bitter sesquiterpene lactones, aromatic oils, and caffeoylquinic acids. In experiments using isolated animal intestinal tissue, yarrow’s flavonoids reduced smooth-muscle contractions primarily by limiting calcium entry into muscle cells. Because calcium helps trigger contraction, this offers a biological explanation for its traditional use for intestinal cramping, although this mechanism has not been confirmed directly in humans. Laboratory research also found that yarrow extracts inhibited neutrophil elastase, an enzyme released by immune cells that can contribute to inflammatory tissue damage. These findings help explain its longstanding use for inflammatory complaints. Traditional uses include poor appetite, bloating, mild digestive cramps, menstrual discomfort, and external applications for minor wounds and irritated skin. Human research provides specific support for menstrual pain: a double-blind, randomized, placebo-controlled trial involving university students with primary dysmenorrhea (painful periods without an underlying pelvic disorder) found that yarrow tea taken during the first three days of menstruation produced significantly greater pain reductions than placebo. These findings PMID: 26238568 specifically concern the tea preparation studied. Its genus name, Achillea, recalls the Greek hero Achilles, who, according to legend, used yarrow to care for soldiers’ battle wounds - a connection preserved in the common name “soldier’s woundwort.”