I have heard various answers to the origin of the phrase to have "hair of the dog" to relieve a hangover. I have heard that it comes from the "fact" that if one is bitten by a werewolf, you had to get a sample or piece if the werewolf's hair and eat it to keep you from turning into a werewolf yourself. I have also heard the same thing applying to a rabid dog, eating a piece of the mad dog's hair. I'm curious to know which, if any, of these explanations is correct, or if there is another explanation
Welcome to the forum heathbug!
For some insights on your question, go here: http://www.waywordradio.org/hair-of-the-politics-that-bit-you/
Read about 6 paragraphs down, and be sure to listen to the audio episode. Lotsa good stuff! I'm pretty sure it will answer your question.