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Why scratching relieves an itch
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February 01, 2008 12:50 IST

Ever wondered why scratching a stubborn itch brings relief and why it is hard to stop? Well, researchers have finally found the clue.

The researchers in the United States have carried out a study and found that scratching is linked to the suppression of unpleasant feelings inside the brain, which actually helps in relieving an itch.

"Our study shows for the first time how scratching may relieve itch. We found that areas of the brain associated with aversive emotions and memories less active during scratching. We know scratching is pleasurable, but we haven't known why.

It's possible that scratching may suppress the emotional components of itch and bring about its relief," lead researcher Gil Yosipovitch at Wake Forest University Baptist Medical Centre was quoted by the ScienceDaily as saying.

The study involved 13 healthy participants who underwent testing with functional magnetic resonance imaging technology that highlights areas of the brain activated during an activity.

The participants were scratched on the lower leg with a small brush. The scratching went on for 30 seconds and was then stopped for 30 seconds -- for a total of five minutes.

The researchers found that reduced brain activity occurred in the anterior cingulate cortex, an area associated with aversion to unpleasant sensory experiences, and the posterior cingulate cortex, which is associated with memory.

When participants reported that the scratching felt most intense, activation in these areas was found to be the lowest.

The imaging results also showed that some areas of the brain were made more active by the scratching, including the secondary somatosensory cortex, a sensory area involved in pain, and the prefrontal cortex, which is associated with compulsive behaviour.

"This could explain the compulsion to continue scratching," Yosipovitch said.

According to him, people occasionally report that intense scratching -- to the point of drawing blood -- is the only thing that relieves chronic itch.

"This is the first real scientific evidence showing itch may be inhibited by scratching. Of course, scratching is not recommended as it can damage the skin. But understanding how the process works could lead to new treatments," he said.

However, one drawback to the study is that the scratching occurred in the absence of itch. The researchers are continuing the study by evaluating whether the findings will apply to chronic itch.

"Understanding more about chronic itch is important," Yosipovitch said.

The results of the study have been published in the Journal of Investigative Dermatology.


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