Okay, it turns out the dog hair dog bite cure was a topical application. I was thinking about it wrong. Which makes sense, that restores at least a little of my faith in these old cranks. I mean, dog hair - that's got to be contraindicated for internal use. It doesn't answer the main question as to how it caught on, but at least it makes the treatment itself seem a lot less cruel. Pretty much harmless, really.
I guess next time I have a hangover though, that means I need to pour a drink over my head?