A bitters is a preparation of herbs and citrus dissolved in alcohol or glycerine with a bitter or bittersweet flavor. The various brands of bitters, once numerous, were formerly manufactured as patent medicines, often serving as digestifs. The few remaining varieties are principally used as aperitifs or as flavorings in cocktails. While bitters commonly have an alcoholic strength of up to 45%, they are normally consumed in small amounts, added as a flavoring agent (similar to vanilla flavoring which is also dissolved in alcohol.)
Common ingredients in bitters include: angostura bark, cascarilla, cassia, gentian, orange peel, and quinine. The flavor of both Angostura bitters and Peychaud Bitters derives primarily from gentian, a bitter herb. Bitters are prepared by infusion or distillation, utilizing aromatic herbs, bark, roots, and/or fruit for their flavor and medicinal properties.