The phrase ‘hair of a dog’ as a cure for a hangover is baffling. It absolutely makes no sense whatsoever and the origin of the phrase refers to an equally baffling decision. The phrase means that it is a good idea to drink more booze to help get rid of a hangover caused by drinking too much booze.
Back in the eighteenth century (the 1700s) the author of a book entitled, The Treatment of Canine Madness suggested that “The hair of the dog that gave the wound is advised as an application to the part injured”. In other words a ‘veterinarian’ should apply hair from the dog to a wound caused by the same dog to treat it.
It sounds crazy, right? Well, it does nowadays but we have to cast our minds back hundreds of years to imagine what it was like then. Before about the middle of the 18th century veterinary medicine did not even exist. It must have been very crude. Knowing this, the treatment described is perhaps understandable.
I am sure that many treatments for dogs, cats and people killed the patients rather than cured them. The same can be said about the “hair of a dog”. Drinking more booze the morning after can only make things worse. Although it might bring temporary relief as the person becomes drunk again.