Why Do Itches Seem to Get Worse When You Scratch Them?

It’s a vicious cycle. You’ve got this itch that just has to be scratched. Then you scratch so hard that it hurts. That’s where the brain comes in, releasing serotonin to calm the pain you’ve created. The unfortunate side effect of all that, scientists have discovered, is that the release of serotonin also activates brain cells called GRPR neurons, which trigger a renewed round of that uncontrollable urge to itch. Researchers at the Washington University School of Medicine in St Louis came to this conclusion in 2014 while studying genetically-modified mice that did not produce serotonin.

Itches, scratches, and serotonin:

• Normal mice injected with a chemical will scratch like crazy. The researchers found that without the serotonin response, the mice had no urge to scratch, thus proving serotonin’s role in the process.
• Could blocking serotonin in humans stop the itch? Maybe, but then they’d have no natural way to control pain. However, there may be a way to stop serotonin from activating the nerve cells in the spinal cord that instigate itch.
• The researchers did identify the nerve receptor known as 5-HT1A as the key to unleashing those itch-specific GRPR neurons in the spinal cord. Their research appeared in the scientific journal Neuron.