Scientists seem to have finally put to rest a longstanding debate over itchiness: Is the urge to itch a sensation that is simply another interpretation of pain, or a separate feeling altogether? It turns out the two stem from different cells and neural pathways, according to a new study in Science. To find out whether pain and itchiness are separate sensations, scientists injected mice with a neurotoxin. This toxin homed in on and killed cells that contained active versions of GRPR, a gene that is involved in the sensation of itchiness. (The same research group discovered this itch gene in 2007.)
Afterward, the mice could no longer respond to any itchy stimuli. They didn't flinch. They made no effort to scratch. But they did respond to pain just like other mice do [TIME], showing that the gene needed to be active to transmit itchiness, but not pain. It's just one ...
