How does a scratch relieve an itch?

“Scientists Discover How Scratching Eases an Itch”

I confess, when I first saw that headline I thought I’d found another hilariously useless study revealing that an itch goes away when scratched.

But the key word in that CBC News headline is “how.” And it’s actually pretty fascinating.

Itching can be prompted by a variety of common health problems and medications. And this sets up another health risk: skin damage and infection caused by chronic itching.

So in an attempt to better understand this most basic human action (itch + scratch = relief), scientists at the University of Minnesota conducted tests with primates in which electrodes were placed on spinal nerves and itching was prompted with histamine injection.

Results showed that scratching suppresses specific spinal cord neurons, which cuts transmission of a signal from the itchy spot on the skin to the brain.

That’s step one. Step two: How do you relieve an itch without scratching?

An “itching expert” told BBC News that a pleasurable scratch sensation to inhibit “itch” neurons might be induced with mechanical stimuli or a drug.

I’d like to cast a vote right now for “mechanical stimuli!” Or rose crystal bracelets, or spine magnets, or voodoo – ANYthing but another drug!

Source:
“Scientists Discover How Scratching Eases an Itch” CBC News, 4/6/09, cbc.ca