The expression, “hair of the dog that bit you” refers to an old method of treating a rabid dog bite by placing hair from the same dog on the wound. We now use it to acknowledge the practice of soothing a hangover (actually alcohol withdrawal) by ingesting the same substance that caused the problem. The earliest known reference to the phrase "hair of the dog" in connection with drunkenness is found in a text from ancient Ugarit dating from the mid to late second millennium.
This metaphor first surfaced in a 1546 collection of English colloquial sayings: “What how fellow, thou knave, I pray thee let me and my fellow have a haire of the dog that bit us last night. And bitten were we bothe to the braine aright.”
Applied to drinks, it means, if overnight you have indulged too freely, take a glass of the same drink to soothe the nerves. "If this dog do you bite, soon as out of your bed, take a hair of the tail the next day." Aristophanes used the Latin 'similia similibus curantur' (like cures like) and it exists today as the basic postulate of classical homeopathy.
During the 1930s, cocktails known as Corpse Revivers were served in hotels.
The Hungarian translation to English is, "(You may cure) the dog's bite with its fur," but has evolved into a short phrase "kutyaharapást szőrével" that is used frequently in other contexts when one is trying to express that the solution to a problem is more of the problem.
Among the Irish and Mexicans, the phrase "the cure, or "curarse la cruda" in Spanish is often used. In Costa Rica the same expression is used but it refers to a pig as in: hair of the same pig.
In some Slavic languages (Polish, Bosnian, Croatian, Serbian, Slovenian and Russian) hair of the dog is called "a wedge" (klin), as in dislodging a stuck wedge with another one, which is used figuratively with regard to alcohol and in other contexts. The proper Russian term is – опохмелка "after being drunk", which indicates a process of drinking to decrease effects of drinking the night before.
In German, drinking alcohol the next morning to relieve the symptoms is sometimes described as ein Konterbier trinken "having a counter-beer." In Austria people have a reparatur-seidl "repair-beer." In Portuguese people speak of uma rebatida "a hit," meaning to strike away the hangover with more alcohol. There is a new Belgian beer called Snuffles and it is brewed exclusively for dogs. Maybe a new term, 'Hair of the Human' will come into vogue.