Dermatology: Scratching An Itch Is Incredibly Rewarding – Here's Why

Have you ever wondered why scratching an itch is so rewarding?

New findings published in the Journal of Investigative Dermatology found that scratching evokes a rewarding and even pleasurable sensation, particularly in patients with chronic itch.

"Chronic itch is a major symptom in dermatological diseases such as atopic eczema and psoriasis and a bothersome symptom in other diseases like end-stage renal disease," said Hideki Mochizuki, PhD, Assistant Professor of Dermatology at TUSM, and first author of the study initiated by Gil Yosipovitch, MD, Chair of Dermatology at TUSM, and Director of the Temple Itch Center, in a news release.

"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," Dr. Mochizuki added. "That is why it is important to understand the cerebral activity that may be inducing this pathological scratching behavior."

This health issue, which is estimated to affect millions of Americans, is defined as itching that lasts for more than six weeks and may even be located over the entire area of the body in some patients.

During the study, researchers induced itching by applying cowhage (a plant) to the right forearms of patients with chronic itch and studying participants without chronic itch as controls. Patients were then imaged using fMRI while they scratched the itch.

Findings revealed that brain activity spiked in the chronic itch patients via supplementary motor area, premotor cortex and primary motor cortex-all areas associated with motor control and motivation to act. Furthermore, brain areas involved in the reward circuit, including the striatum, cingulate cortex, caudate nucleus and orbitofrontal cortex, were significantly more activated than in healthy subjects.

"Chronic itch is a major symptom in dermatological diseases such as atopic eczema and psoriasis and a bothersome symptom in other diseases like end-stage renal disease," added Hideki Mochizuki, PhD, Assistant Professor of Dermatology at TUSM, and first author of the study initiated by Gil Yosipovitch, MD, Chair of Dermatology at TUSM, and Director of the Temple Itch Center.

"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," Dr. Mochizuki concluded. "That is why it is important to understand the cerebral activity that may be inducing this pathological scratching behavior."

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