Several hundred experts in itch from all over the world are meeting in San Francisco this week to talk about everything from that little itch on your back to chronic itchiness that leaves sufferers unable to sleep.
"We want to help people realize that itching can be really severe and a terrible problem, almost as bad as chronic pain," said Earl Carstens, a professor of neurobiology, physiology and behavior at UC Davis who is organizing the Fourth International Workshop for the Study of Itch, which began Sunday at the Hilton San Francisco. "It's not usually life threatening, but it can be. I've read about cases of people who have such severe chronic itching that it drives them to suicide."
Everyone gets itchy sometimes, and most people have experience with some form of acute itchiness - chicken pox, perhaps, or a run-in with poison oak. Few studies about rates of chronic itch exist, but researchers estimate between 15 million and 31 million Americans have a form of atopic eczema, in which allergies cause itchy, inflamed skin.
Little is known about what makes people itch. The minor everyday itches everyone gets are usually caused by simple brushes with small irritants - a fly landing on a hand or a scratchy fabric in one's shirt. Sympathetic itch - the need to scratch when witnessing someone else scratch - probably happens because of an increased awareness of our own bodies.
No one knows for sure why people get itchy, but the main theory is that it's an evolutionary trait - we get itches so we'll scratch away something that irritates our sensitive skin, be it a mosquito or a hand cream that causes an allergic reaction. But that doesn't explain chronic itch.
For decades, researchers assumed itch was a minor form of pain, attached to the same nerves that make us feel pain. But research in the past five or so years has suggested that itch may have a separate nerve pathway.
Some doctors have suggested a sort of yin-and-yang relationship between itch and pain - scratching, a very mild form of pain, alleviates itch, and certain pain-relieving drugs cause itching.
"Pain and itch are different responses, but they're both geared toward protecting you," Carstens said. "You have distinct systems. One, itch, is evolved to get stuff off the surface of your skin, and the other, pain, is to remove yourself from something that is causing damage."