Why Scratching Stops an Itch

When you get an itch, you scratch it. But why does that make the itch go away?

For the first time, researchers from the University of Minnesota have figured it out!

Scratching relieves an itch because it blocks activity in some spinal cord nerve cells that transmit the sensation to the brain, reports the BBC News. But the effect only works when we feel an itchy sensation. Scratching at any other time makes no difference.

Although previous research suggested that a specific part of the spinal cord called the spinothalamic tract played a key role, until now, scientists knew very little about the physiological mechanisms of scratching an itch.

Led by Dr. Glenn Giesler, the Minnesota study found that scratching the skin blocks activity of nerve cells in the spinothalamic tract during itchiness, preventing the spinal cord from transmitting signals from the scratched area of the skin to the brain, reports the BBC.

We itch for reasons known and unknown. For most types of itching, there is no particular cause, and it doesn't even serve a clear purpose; however, more than 50 diseases cause itching, including shingles, chicken pox, liver disease and kidney failure.

"We all know that scratching helps alleviate itch, but this elegant study helps to show how this mechanism works," Patrick Haggard of University College London told the BBC. "It's an interesting illustration of a very general principle of the brain controlling its own inputs, in this case by making movements that trigger an interaction between scratchy touch and itch."

The study findings were reported in the journal Nature Neuroscience.

--From the Editors at Netscape

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