ITCHINESS COMES FROM YOUR BRAIN.

It’s long been believed that humans experience itchiness so that we can keep harmful irritants—like insects—at bay (when we scratch an itch, it makes that pesky pest leave our skin). But this explanation still doesn’t answer the question of how your body gets itchy. Recent research shows that when your skin comes into contact with an external irritant, it sets off a complex chain of reactions that stretch from itch receptors in your skin to your spinal cord to your brain. Nerve cells far from the irritation site release specialized molecules that tell your brain it’s time to scratch. Scratching relieves itchiness, scientists believe, because it creates a mild pain—which researchers now know is a distinct sensation from itchiness—that replaces the itch.