Researchers at the University of Lubeck in Germany have shown that a mirror illusion can fool people into feeling relief from an itch, even when they scratch the wrong place.
Perception of our own bodies can be easily manipulated, using tricks such as the rubber hand illusion, which fools people into thinking a rubber hand is their own, researchers said.
Reflecting someone's limb in a mirror has also been used to treat phantom limb pain, they said.
Christoph Helmchen and his colleagues injected the right forearms of 26 male volunteers with itch-inducing chemical histamine. Since the injection creates a red spot, they painted a corresponding dot on the opposite arm so both looked identical.
One of the researchers then scratched each arm in turn. Scratching the itchy arm produced relief, while scratching the other one did not, 'New Scientist' reported.
Then, they placed a large vertical mirror in front of the itchy arm, blocking off the subject's view of their right arm and reflecting back the non-itchy one in its place.
Volunteers were told to look only at the reflected limb in the mirror, while a member of the team again scratched each arm.
This time the participants felt relief when the unaffected, reflected arm was scratched. Although the effect was relatively weak the relief from mirror scratching is about 25 per cent of that from scratching the real itch the study showed that visual signals to the brain can override messages from the body if there is a mismatch between them, researchers said.