You will probably not be able to read this piece without feeling a little itchy. I apologise in advance.

In a laboratory at the National Institutes of Health, Santosh Mishra and Mark Hoon have bred a group of mice with an enviable super-power—they’re immune to itching. You can dab their skin with substances that would send most of us into a scratching frenzy, and they’ll be completely unfazed.

Compared to normal mice, these rodents are missing just one gene called Nppb. It produces a similarly named neuropeptide—a protein fragment that neurons use to communicate with each other. If you inject mice with Nppb, they scratch furiously. If you remove the gene for it or kill the neurons that make it,