In a fascinating Ted Ed lesson based upon the work of educator Emma Bryce and animated by Sashko Danylenko, a narrator explains the physiological reasons behind skin itches, what causes itching and how the act of scratching an itch is really a distracting misdirections that tricks the brain into feeling a sense of relief.
Researchers have discovered that itch signals in their skin are transmitted via a subclass of the nerves that are associated with pain. These dedicated nerves produce a molecule called natriuretic polypetide B, which triggers a signal that’s carried up the spinal cord to the brain, where it creates the feeling of an itch. When we scratch, the action of our fingernails on the skin causes a low level pain signal that overrides the itching sensation. It’s almost like a distraction, which creates the sensation of relief.