Scratching Makes You Itch More, and Here's Why

We've long known that at least in the case of most rashes, if you scratch it, you'll just make it worse. However, that fact, a common warning from mothers everywhere, actually applies to all itches, no matter how small, according to a new study. Why is it that moms have to be right all the time?

The study, recently published in the journal Neuron, details how scratching an itch can actually intensify the annoying sensation.

So why do we scratch in the first place? We all must have learned early in our lives that scratching a spot can at least temporarily relieve an itch. That's because mild pain in the skin can override what neurons around the itch are feeling.

"The problem is that when the brain gets those pain signals, it responds by producing the neurotransmitter serotonin to help control that pain," senior researcher Zhou-Feng Chen of Washington University in St. Louis explained in a recent release. "But as serotonin spreads from the brain into the spinal cord, we found the chemical can 'jump the tracks,' moving from pain-sensing neurons to nerve cells that influence itch intensity."

This was determined after Chen and his colleagues bred a strain of mice that lacked the genes to make serotonin. When these mice were injected with a serum that produces a mild itch, they didn't scratch nearly as much as standard lab mice. However, when these mice were then given supplemental serotonin, they scratched just as much, indicating that the scratching was actually making the itch worse in the long run.

Now here's where things get interesting. Chen, the director of the Center for the Study of Itch (yes, that's an actual facility), explained that blocking serotonin to relieve an itch is impractical because the chemical is also involved in processes like growth, aging, and even mood regulation.

Instead, researchers at the center suggest that it might be possible to interfere with the communication between serotonin and nerve cells in the spinal cord that specifically transmit itch. After a series of animal trials, they found that nerve receptors known as 5HT1A are the key to activating the itch-specific neurons in the spinal cord.

Blocking this receptor off resulted in mice again scratching less when itchy.

"We always have wondered why this vicious itch-pain cycle occurs," Chen said.

Now he not only has an answer, but a potential solution for the most maddening of itches.