As seen in Kingdom of Heaven and mentioned in Hamlet.
What sort of poison is best applied through the ear canal and where does it go from there to kill a person.
I have a vague recollection of hot lead. Which would probably kill you.
Dunno if it counts as a poison, though.
I thought hot lead was inserted into your rear passage so as to burn you to death internally without leaving marks outside the body? (Or so unkind tales of Kings of England would have you believe)
My Shakespeare teacher in high school said people in The Bard’s day thought you could be poisoned through your ear, but you really can’t. But then, my prof wasn’t an M.D.
An earlier thread on the topic: Poison in your ear - Factual Questions - Straight Dope Message Board
There are poisons which can be applied topically, so I don’t see why they wouldn’t work in the ear. Certainly you could drug someone via an LSD solution in the ear (though I doubt you would be able to kill them). You may be able to kill someone by introducing a high concentration of nicotine into the ear.
You could also inject a poison into the bloodstream, and do it through the ear so that the injection wound wouldn’t be noticeable. Almost all poisons will work injected.
It’s highly goubtful that you’d remain asleep if someone started pouring poison in your ear, though, and there are far easier methods of killing you with poison.
Poison in the ear should also be understood as a metaphor for saying bad things about people.