Why Is Scratching So Pleasant?

Ooh! Aah! Even a tree bark would be good for that back itch. Scratching is something that can escape your control, and eventually damage your skin. Now, a research published in the "Journal of Investigative Dermatology" explains what's going on in our brain when we scratch. The team at the Wake Forest University Baptist Medical Center has used for this study functional magnetic resonance imaging (fMRI) scans, which display the activation of brain nuclei.

"Our study shows for the first time how scratching may relieve itch. For some people, itch is a chronic condition that affects overall health," said lead author Dr. Gil Yosipovitch, a dermatologist who specializes in itch.

The 13 healthy volunteers were scratched on the lower leg with a small brush for 30 seconds, and after a pause of 30 seconds, again, and this for a total of 5 minutes.

"To our surprise, we found that areas of the brain associated with unpleasant or aversive emotions and memories became significantly less active during the scratching. It's possible that scratching may suppress the emotional components of itch and bring about its relief," said Yosipovitch.

The most inhibited nuclei by scratching were the anterior cingulate, connected with aversion to unpleasant sensations, and the posterior cingulate, connected to unpleasant memories. The intenser the scratching, the more inhibited these nuclei were.

"Patients 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 that itch may be inhibited by scratching. Of course, scratching is not recommended because it can damage the skin. But understanding how the process works could lead to new treatments. For example, drugs that deactivate this part of the brain might be effective," said Yosipovitch.

Instead, the activity of other brain nuclei was boosted by the scratching, like the secondary somatosensory cortex, connected to pain, and the prefrontal cortex, connected to compulsive behavior.

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

Still, the research was made on patients who did not experience an itch and were only scratched.

"Understanding more about chronic itch is important. More than 30 million Americans suffer from eczema and almost half (42%) of kidney dialysis patients are bothered by moderate to severe itch. In fact, those kidney dialysis patients with itch have a 17% higher mortality rate, likely from a loss of sleep," signaled Yosipovitch.