The herb vervain is a common perennial wildflower in England, found growing at the edge of roads and in meadows. It has a long history of use in Celtic religious tradition, and has been used as medicine by many cultures. The leaf and flower are the parts used medicinally.

Like other bitter plants, vervain has been used to stimulate appetite and digestion. Other traditional uses include treating abdominal spasms, fevers, depression (especially following illness or childbirth), and inadequate flow of breast milk.

Vervain is commonly recommended today to increase flow of breast milk, as well as to treat insomnia and menstrual pain. However, there is no meaningful evidence to support any of these uses.

One study in rats found possible sedative effects with a vervain extract.1 A test-tube study found hints of potential anti-cancereffects.2 However, evidence like this is far, far too preliminary to show efficacy. Only double-blind, placebo-controlled studies can prove that a treatment really works, and no studies of this type have been performed on vervain. (For information on why such studies are essential, seeWhy Does This Database Rely on Double-blind Studies?)