This itch-triggering protein also sends signals to stop scratching

People who can’t stop scratching itches may finally have a culprit to blame.

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Gualdani’s team genetically engineered mice to lack TRPV4 in certain nerve cells. Those mice reacted to pain just like mice that have intact protein.

Then the team rubbed a vitamin D–like substance on the mice to mimic eczema, a chronic inflammatory skin condition that affects about 10 percent of people in the United States and leads to itchy, dry skin and rashes. Mice that make TRPV4 had many brief bouts of scratching. Mice that lack the protein in their nerves don’t scratch so often, suggesting that TRPV4 is involved in triggering itch. It’s not the only molecule involved so the mice did still get itchy sometimes.

When mice without the protein do scratch they “have a very, very long episode of scratching before [they] stop. So this is a suggestion that they have lost the regulatory mechanism that caused the relief from scratching,” Gualdani says.

The findings could be important for understanding chronic itching in people. Eventually, the knowledge may lead to treatments for eczema and other itchy skin conditions. But it’s a delicate balance, Gualdani says. Substances that turn off TRPV4 may make itching less frequent, but dialing back the protein’s activity too much could mean people would have a hard time stopping scratching once they start. Conversely, upping the protein’s activity may relieve stubborn itches, but could lead to even more frequent itching and scratching.