CHICAGO, ILL. — If you hate getting your hair brushed, it’s probably because it hurts so much when the bristles hit a tangle. That painful zing travels faster than most any other type of pain. It zips down a nerve fiber at some 160 kilometers (100 miles) an hour.
That finding was presented here, October 8, at the annual meeting of the Society for Neuroscience. It shows a new way our bodies sense and respond to different sorts of hurt.
Pain can come from many mishaps. Cuts, jabs, pinches, cramps, bites, slaps — even stubbing your toe in the dark. They all hurt, but each feels different.
Pain is our bodies’ way of warning us when it’s being harmed. So it’s not surprising we have many different ways of sensing pain. “Because when it doesn’t,” says Gregory Dussor, “we don’t live.” A neuroscientist, he works at the University of Texas at Dallas and did not take part in the new study.
In the new work, researchers conducted laboratory tests on the pain of hair-pulling. A hair pull was about 10 times as painful as a pinprick, reported Emma Kindström of Linköping University in Sweden. Her group also found that the pain was detected by a large, propeller-shaped protein known as PIEZO2.
That was a surprise.
Scientists knew PIEZO2 detects pressure, including light touches. It wasn’t thought to detect sudden, sharp pain. But people who lack this protein don’t feel hair-pull pain.
A hair-pull sends a pain signal along nerve fibers much faster than other sorts of pain, Kindström says. In fact, she reports, it travels through a different type of nerve fiber, called A-beta. Other kinds of pain signals, such as a burn from a hot stove, travel far more slowly and along different kinds of fibers.
People probably vary in how much hair pulling hurts, she says. “Some people enjoy taking a very, very hot shower, while some people find it very painful. I don’t see why hair pulling would be different.”
She sees this sort of difference in her pet dogs. One of them, Harry, doesn’t mind getting brushed. But Norton, the other? He’s very sensitive to fur pulling. And he reacts — with a bite.
