Wiktionary
unscratchable
a. Not scratchable; impossible to scratch.
Usage examples of "unscratchable".
His silence drives me crazier than the unscratchable itch on the ball of my injured foot.
The need to open his eyes was an overwhelming frustration, like an unscratchable itch.
He twists his butt in the chair, as if he's got an unscratchable itch.