I have a lump behind my ear, which seems to be far enough under the scalp. However, when I first noticed it, I rubbed it and doing so gave me an electric shock. I have since stopped doing this as it is not very comfortable or of any benefit. When just gently placing my finger down on it I can move the lump around, with no electric shock, so it is only when I either rub it or tap it with my finger.
Why is this?
An answer would be greatly appreciated.