Pain and itch evoke very different responses. Pain invites withdrawl, leading the body to retract and protect any endangered part of itself. Itch stimulates the need to scratch, a reflex that draws all focus to the affected skin site. Controlled by the part of the brain largely responsible for reward and decision making, scratching brings with it the promise for relief. This promise is not always fulfilled. If the source of an itch is not physically removed - ie. an insect removed from the skin - scratching can actually increase irritation, leading to an uncontrollable, relentless, hedonic need to scratch.