Neuroscientists have long scratched their heads to solve the puzzle of itching. But now researchers have finally worked out what makes us itch.
The research team, led by neuroscientist Zhou-Feng Chen and his colleagues at Washington University in St Louis, Missouri, has identified cells in the spinal cord that spring into action when an insect bite, washing powder or infection irritates our skin.
These cells transmit the message to brain, which then tells the body it is time to start itching, reports the journal Nature.
Chen said: "Most people accept that there are specific, highly specialized neurons for sensations like taste. But for pain and itch this is much more controversial. This is the first time itch perception has been shown to be independent from pain."
Early research has found why it feels so good to scratch an itch. Scratching numbs the part of the brain linked to unpleasant thoughts and memories.
It also raises activity in brain regions related to compulsion- perhaps explaining why we sometimes can't help but scratch and scratch.