There is nothing more primitively satisfying that scratching an itch. Babies, dogs, monkeys and people with crabs do it like their lives depend on it. It’s one bodily function that you don’t have to work hard to accomplish, and you don’t have to agonize over the consequences or make any kind of decision beyond the simple brain-to-hand order “scratch.” For most of us, scratching an itch is a simple endeavor that gives an immediate reward: itch relief.
Here’s a shocker: It’s not your skin that’s making you itch, nor is it your skin that’s getting relief when you scratch. All of that itching and scratching business is controlled by a specific set of neurons in the spinal cord.