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Carry on scratching

Friday 1 February 2008

“Doctors have put their finger on why it feels so good to scratch an itch,” the Daily Mail reported today. Many newspapers covered an American study that used an MRI scanner to look at how our brains react when people scratch. The Daily Telegraph said that the study showed that “scratching makes the part of the brain associated with unpleasant feelings less active, bringing about the feeling of relief”.

BBC News quoted the scientists as suggesting, “It's possible that scratching may suppress the emotional components of itch and bring about its relief.” These findings are hoped to be useful in developing new treatments for people with chronic itchy skin conditions.

This study was carried out in 13 healthy volunteers, and not in people with any of the conditions associated with chronic itching. Although it contributes to understanding in this area, the complex brain mechanisms underlying this process have only recently begun to be investigated. More studies are needed to investigate itching and scratching in people with skin diseases, before scientists can use this knowledge to suggest new treatments.

Where did the story come from?

Professor Gil Yosipovitch and colleagues from the Wake Forest University School of Medicine, North Carolina, USA carried out the research. The study was funded by the Center for Biomolecular Imaging of Wake Forest University Health Sciences. The study was published in the peer-reviewed: The Journal for Investigative Dermatology.

What kind of scientific study was this?

This was an experimental study carried out in 13 healthy volunteers. The volunteers were placed into a magnetic resonance imaging (MRI) scanner to look at the activity in their brain. After 60 seconds in the scanner, the skin on their lower left leg was scratched with a small brush by a researcher for 30 seconds, followed by 30 seconds that were free of scratching. This was repeated a number of times. The volunteers reported that the sensation was similar to how it felt when they scratched themselves and that the scratching was not painful. The researchers then compared brain activity during periods of scratching with periods free from scratching.

What were the results of the study?

The researchers found that during scratching, there was an increase in the activity in certain areas of the brain (the second somatosensory cortex, insular cortex, prefrontal cortex, inferior parietal lobe, and cerebellum). Some of these areas are involved in the sensation of pain and touch, mood and attention, and habit learning. There was a reduction in activity in other areas of the brain during scratching (the anterior and posterior cingulated cortices). These areas are involved in emotional and cognitive processing, and memory.

What interpretations did the researchers draw from these results?

The researchers concluded that their study has identified areas of the brain that are activated and deactivated by repetitive scratching.

What does the NHS Knowledge Service make of this study?

This study adds to understanding of the effect of scratching on the brain, but can be viewed as only the first step. Important points to note about this study are:

  • It was carried out on healthy volunteers who did not have chronic itchy skin conditions. The response to scratching in healthy people may be different than the response in those with itching conditions. The authors acknowledge that further studies looking at scratching in chronic itch conditions are needed, and will be more clinically relevant.
  • The volunteers did not scratch their legs themselves and the scratch was not in response to an itch; the areas activated in a person scratching their own itch may differ.

This type of research does not immediately suggest treatments for the conditions studied, but knowing more about the brain mechanisms that underlie itching and scratching may be helpful in the long term.

Analysis by Bazian
Edited by NHS Website

Links to the headlines

It's all in the mind? why a good scratch feels so satisfying.

The Scotsman, 1 February 2008

How scratching impacts on brain.

BBC News, 1 February 2008

If you've got an itch, here's why you have to scratch it.

The Times, 1 February 2008

Why we are all itching to read this research.

The Daily Telegraph, 1 February 2008

Links to the science

Yosipovitch G, Ishiuji Y, Patel TS, et al.

The Brain Processing of Scratching.

Journal of Investigative Dermatology 2008 Jan 31[Epub ahead of print]