system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we itch?

What’s happening in our bodies when we get that really deep itch that we can’t get? Is it a misfiring nerve? (I’m not asking about the itch you can get rid of by scratching - I mean when you scratch and scratch and there’s no relief)
gpt
The underlying cause of an itch, believe it or not, is not too well understood. While typically a stimulus will cause you to react and itch, It will probably be due to a reason. Constant itching can be due to irritated skin from a toxin or other reagent that causes a stimulus. In our bodies we have whats called tonic and phasic receptors. A phasic receptor is a receptor that will respond to a stimulus and adapt if is a constant stimulus. (Like our shirts constantly touching us, but we ignore it eventually) A tonic receptor will respond as long as the stimulus persists. Pain and itch come from the same type of receptor, where it will continue to signal until the stimulus stops (tonic).