Bitters were first formulated by 18th century physicians (and hacks) and sold as medicinal tonics. Most were a mix of herbs and spices preserved in alcohol. Many bitters were marketed toward those suffering from issues with circulation or digestion, such as Hostetter's Stomach Bitters and Burdock's Blood Bitters. Because bitters typically tasted bad, many people began mixing them with a spirit. By 1806, the word “cocktail” was being used to describe a mix of spirits, water, sugar, and bitters. By the close of the 19th century, bartenders such as cocktail pioneers Jerry Thomas and Harry Johnson had begun using bitters to make mixed drinks. Cocktail bitters became far less commonplace in America in the 20th century due to Prohibition as well as changing tastes and drinking habits. Bartender and author Gary Regan is credited with bringing back bitters in 2005 when he introduced Regan's Orange Bitters No. 6. Soon after, bartenders across the country began mixing drinks with cocktail bitters once again. Two brands had survived from the 1800s, Angostura and Peychaud's, and they are considered classics today. Another brand called Fee Brothers dates back to the 1950s. With the cocktail bitters resurgence in the mid-2000s, several new brands popped up to meet the growing demand. Today, cocktail bitters come in many varieties, including classics like orange bitters and newer versions like celery bitters and grapefruit bitters.