Got an itch you just can’t scratch? Try looking in the mirror to fool your brain, say scientists



Next time you struggle to stop yourself scratching a rash or itch, the key could be to look into the mirror, scientists say.

German researchers have discovered that the brain can easily be fooled into thinking relief is at hand.

In a series of experiments using large mirrors, the team found scratching the opposite side of your body in a mirror was just as effective.

Christoph Helmchen and his colleagues at the University of Lübeck in Germany found that a similar mirror illusion can fool people into feeling relief from an itch, even when they scratch the wrong place.

They found that although the effect was about 25% as effective as a ‘real’ scratch, the effect still brought relief.

‘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,’ the researchers concluded.

‘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.’

The team injected the right forearms of 26 male volunteers with itch-inducing chemical histamine.

Because 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.

Next, 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.

They asked the volunteers to look only at the reflected limb in the mirror, whilst 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 a quarter of that from scratching the real itch – the study shows that visual signals to the brain can override messages from the body if there is a mismatch between them.


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