When you have an itch on one arm, scratching the other arm can actually relieve the itch!

When you have an itch, you should scratch it. But what if you have a disease like eczema, where scratching can make everything worse? Enter these scientists, who set out to determine whether your brain can be tricked into thinking an itch has been scratched when it hasn't. First, they "experimentally induced" itching by injecting histamine (eek!) into a subject's right arm. Then, they scratched the subject's left arm while holding up a mirror, which made it appear that the right arm was being scratched. And it worked! "Scratching the non-itching limb attenuated perceived itch intensity significantly and selectively in the mirror condition, i.e., when the non-itching forearm was visually perceived as the itching limb." So the next time you scratch an itchy mosquito bite until it bleeds, stop -- and try a mirror instead!Itch Relief by Mirror Scratching. A Psychophysical Study "Objective The goal of this study was to test whether central mechanisms of scratching-induced itch attenuation can be activated by scratching the limb contralateral to the itching limb when the participant is made to visually perceive the non-itching limb as the itching limb by means of mirror images. Methods Healthy participants were asked to assess the intensity of an experimentally induced itch at their right forearm while they observed externally guided scratch movements either at their right (itching) or left (non-itching) forearm which were either mirrored or not mirrored. In the first experiment, a mirror placed between the participant’s forearms was used to create the visual illusion that the participant’s itching (right) forearm was being scratched while in fact the non-itching (left) forearm was scratched. To control visibility of the left (non-mirrored) forearm, a second experiment was performed in which unflipped and flipped real-time video displays of the participant’s forearms were used to create experimental conditions in which the participant visually perceived scratching either on one forearm only, on both forearms, or no scratching at all. Results In both experiments, scratching the non-itching limb attenuated perceived itch intensity significantly and selectively in the mirror condition, i.e., when the non-itching forearm was visually perceived as the itching limb. Discussion These data provide evidence that the visual illusion that an itching limb is being scratched while in fact the non-itching limb contralateral to the itching limb is scratched, can lead to significant itch relief. This effect might be due to a transient illusionary intersensory perceptual congruency of visual, tactile and pruriceptive signals. “Mirror scratching” might provide an alternative treatment to reduce itch perception in focal skin diseases with persistent pruritus without causing additional harm to the affected skin and might therefore have significant clinical impact." Related content: Science that makes you itchy just thinking about it.Psychologists can give you false memories of having committed a crime.NCBI ROFL: Absolut memory distortions: alcohol placebos influence the misinformation effect.