The experiment was not for the squirmish. Volunteers were made to itch like crazy on one arm, but not allowed to scratch. Then they were whisked into an MRI scanner to see what parts of their brains lit up when they itched, when researchers scratched them and when they were allowed to scratch themselves. The scientific question was this: Why does it feel so good to scratch an itch?
“It’s quite intriguing to see how many brain centres are activated,” said Dr Gil Yosipovitch, chairman of dermatology at the Temple University School of Medicine and director of the Temple Center for Itch. “There is no one itch centre. Everyone wants that target, but it doesn’t work in real life like that.”
Instead, itching and scratching engage brain areas involved not only in sensation, but also in mental processes that help explain why we love to scratch: motivation and reward, pleasure, craving and even addiction. What an itch turns on, a scratch turns off — and scratching oneself does it better than being scratched by someone else. The study results were published in the journal PLOS One.
Itching was long overshadowed by pain in both research and treatment, and was considered just a mild form of pain. But millions of people suffer from itching, and times have changed. Research has found nerves, molecules and cellular receptors that are specific for itching and set it apart from pain, and the medical profession has begun to take it seriously as a debilitating problem.
Within the last decade, there has been a flurry of research into what causes itching and how to stop it. Along with brain imaging, studies have begun to look at gene activity and to map the signals that flow between cells in the skin, the immune system, the spinal cord and the brain.
The concern is not so much the fleeting nastiness of mosquito bites and poison ivy, but the misery caused by chronic itching and that often resists remedies.
For the first time in the US, itching research and treatment centres have opened. “Itch is now where pain was probably 20 years ago,” said Dr Lynn Cornelius, chief of the dermatology division at Washington University School of Medicine. “The science has to lead to treatment, I believe. Clinicians won’t just look upon someone itching as someone who needs antihistamines.”
Itching appears widespread in the animal kingdom — though