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Scraching that Itch

November 12, 2014

Scientists have identified the cruel trick the brain plays that may explain why scratching an itch often makes it itch even more.



4433307491_30232e06ed_z Jessica Lucia Flickr

The urge to scratch an itch can be hard to resist. (Jessica Lucia/Flickr)

An itchy, scratchy Catch-22. I’m Bob Hirshon and this is Science Update.

Science has now confirmed that scratching an itch will indeed just make it itch even more. Neuroscientist Zhou-Feng Chen works at Washington University’s Center for the Study of Itch. He says itching is an evolutionary survival mechanism, telling us when something dangerous like a mosquito is lurking on our skin.

ZHOU-FENG CHEN (Washington University):

And you feel something and then you scratch it away so that you protect yourself.


Scratching produces minor pain, which temporarily distracts you from your itch. To reduce the pain, the brain helpfully releases the brain chemical serotonin. But here’s the catch: serotonin very likely causes even more itching, followed by more scratching.


So this is the cause of the vicious itch-scratch cycle.


The team verified this by artificially inducing scratching in lab mice with injections of serotonin. They report their findings in the journal Neuron. I’m Bob Hirshon, for AAAS, the science society.