Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Cold, dry winter weather can wreak havoc on our skin, drying it out and making us feel like one giant itch. Yet when it comes to scratching all of those dry patches, something inside our brains signals when it’s time to stop. That moment of relief is not accidental, and scientists have now pinpointed the key mechanisms behind it. The findings are being presented this weekend at the 70th Biophysical Society Annual Meeting in San Francisco, California.  Outside of winter, chronic itch affects millions of people with conditions including eczema, psoriasis, and kidney disease. Understanding the precise biological mechanisms that regulate itch—including what tells us to stop scratching before we get hurt—could help scientists develop better treatment. In the new study, researchers from the University of Louvain in Brussels, Belgium, found an unexpected role in a specific ion channel. These channels in the body allow ions—atoms with an electrical charge—to flow in and out of the neuron’s membrane in …