Bitters are an alcoholic herbal preparation with a bitter or bittersweet flavor. Many bitters, once numerous, were formerly manufactured as patent medicines, often serving as digestifs. The few remaining varieties are principally used as apéritifs or as flavorings in cocktails. Bitters commonly have an alcoholic strength of up to 40%.

They are not to be confused with bitter, a type of British ale.

Common ingredients in bitters include: angostura bark, cascarilla, quassia, 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.

Angostura Bitters was first compounded in Venezuela in 1824 by a German physician, who intended it as a remedy for stomach maladies. It was exported to England and to Trinidad, where it came to be used in a number of cocktails following its medicinal use by the British Navy in Pink Gin. Angostura and similar gentian bitters preparations are still of some value to settle a mild case of nausea, and is used to stimulate the appetite, either for food or cocktails. It is used in both apéritifs and digestifs, and will settle one's stomach before a meal, or before undertaking a night of drinking. In fact, a bitters and soda will cure normal gastral ailments.

Their use in cocktails, however, is what accounts for the vast majority of sales. Angostura was named for the town of Angostura in Venezuela. It contains no angostura bark, a medicinal bark which is named after the same town. Angostura Bitters is the most widely distributed bar item in the world.

Used as the "starter" ingredient in a Pink Gin, where a splash (or two) of Angostura Bitters is swilled around the inner surface of a tumbler before adding a generous measure of London Gin. The resulting drink is so named from the colour imparted by the Bitters. In addition to the options of drinking a Pink straight, it may also be consumed with a little water, still or sparkling. Real connoisseurs of the Pink Gin even have preference for drinking it "in" or "out" - referring to whether the remaining dribble of Bitters (after the glass has been "pinked") be left in or poured away, before the Gin is added.

A large tumbler, similarly "pinked", and filled with sparkling lemonade, results in a drink known as a Campbell. This is a pleasant and refreshing way the relieve a little of the sweetness of lemonade, and is of sufficiently low alcohol content to be served to youngsters as "something special" when they are with parents at a cocktail party or similar.

Peychaud's Bitters is associated with New Orleans, Louisiana, and can be difficult to find elsewhere. It, too, is a gentian based bitters, with a subtly different and sweeter taste than the Angostura brand. Peychaud's Bitters is associated with the Sazerac cocktail.

Orange bitters are made from the rinds of unripe oranges. They are called for in some older cocktail recipes; traditionalists consider orange bitters to be an essential ingredient in the Martini.

Medicinal quantities of quinine were occasionally used in old cocktail recipes. Quinine is still found in much lower concentrations in tonic water, used today mostly in drinks with gin.

Types and brands

Bitters still available today include:

Angostura Bitters (from Trinidad and Tobago)
Bénédictine (from France)
Becherovka (from Czech Republic)
Campari (from Italy)
Chartreuse (from France)
Martini & Rossi ChinaMartini (from Italy)
Fernet Branca (from Italy)
Galliano (from Italy)
Gammel Dansk (from Denmark)
Jägermeister (from Germany)
Mint bitters
Orange bitters
Peach bitters
Peychaud's Bitters (from Louisiana, United States)
Underberg (from Germany)
Unicum (from Hungary)
Fee's bitters (aromatic, orange, and peach), from Rochester, New York; the aromatic bitters contain Angostura bark
Beerenburg (from Holland)

Other brands/types of bitters have also included:

Amer Picon (from France)
Appenzeller (from Switzerland)
Averna (from Italy)
Boker's
Boonekamp's (from Germany)
Calisaya bitters (containing cinchona/quinine)
Echt Stonsdorfer (from Germany)
Hostetter's
Kabänes (from Germany)
Kuemmerling (from Germany)
Licor 43 (from Spain)
Maraschino bitters
Meyer's Bitter (from Germany)
Flimm´s (from Germany)
Ramazzotti (from Italy)
Ratzeputz (from Germany)
Reichs-Post Bitter (from Germany)
West Indies