The common hop plant is an herbaceous perennial native to Europe and cultivated in temperate regions throughout the world. The vine stems of the plant, which are produced new annually, reach up to 10 meters in length and retain a pliable, non-woody consistency. The leaves are opposite and serrate with three to five lobes apiece. Male and female flowers are produced on separate plants. The greenish-yellow male flowers are small and inconspicuous, measuring about 5 millimeters in diameter. The female flowers bloom in heavily blossomed, branched clusters, eventually producing cone-like fruiting bodies called hops, which are harvested and dried for use in the brewing of beer and for health purposes.
Hops' most active constituent is generally believed to be its volatile oil, which is itself very complex in makeup, containing several unstable compounds that break down quickly, causing wide variances in potency over time. Hops also contain bitter acids, resins, phenolic compounds, tannins, and flavonoids, which may contribute to the herb's activity.
The dosage approved by Commission E is 1/2 gram of dried hops per day. While there are no known health hazards associated with hops at this dosage, allergic reactions may occur in some sensitive individuals.