The pleasure that people receive by scratching an itch is due to "overactivity" in the areas of the brain involved in motor control and reward processing, says a new study conducted at Temple University School of Medicine in the US.
"Despite being pleasurable at first, ongoing scratching can lead to an increase in the intensity of itch as well as pain and permanent skin damage," said first author of the study Hideki Mochizuki, assistant professor of dermatology.
"That is why it is important to understand the cerebral activity that may be inducing this pathological scratching behavior," Mochizuki said.
Using advanced functional magnetic resonance imaging (fMRI), the researchers looked at activity in the brain while 10 chronic itch patients and 10 healthy participants scratched an itch.
They found that areas of the brain involved in motor control and reward processing were more activated in chronic itch patients while they scratched.
This overactivity may help explain the addictive scratching experienced by these patients says the study published in the Journal of Investigative Dermatology
During the study, itch was induced by applying cowhage (a plant) to the right forearms of patients with chronic itch and study participants without chronic itch.
"Our findings may enable us to identify and advance the understanding of the brain network underlying the itch-scratch cycle in chronic itch patients. This understanding could lead to new therapies for these patients," Mochizuki added.