Scientists believe they have identified the gene for itchiness, raising the hope of treatment for the condition.
People with eczema suffer from itchiness
The GRPR "itch gene" was found in spinal cord nerve cells by a Washington University team.
The researchers, who carried out tests on mice, say it is responsible for relaying itch signals from the skin to the brain, via the spinal cord.
They say if they are right, it may hold the key for helping people with severe itching, the Nature journal reported.
Chronic itching can be caused by skin disorders like eczema or can stem from deeper problems such as kidney failure or liver disease.
It can also be a serious side-effect of cancer therapies or powerful painkillers like morphine.
In the most serious cases it can lead to sleep problems and scarring, and yet researchers say there is little treatment available for it.
Historically, scientists have regarded itching as a less intense version of pain and have tailored their research to understanding pain.
In fact, it was during such research that the GRPR (gastrin-releasing peptide receptor) gene first came to the scientists' attention.
The gene stood out as they noticed it was only present in a few spinal cord cells, but after carrying out tests on mice they realised it was not related to the pain pathway.
However, they did find it had an impact when itching tests were carried out. Mice who had the gene neutralised did not react as much as those with the gene when given itchy stimuli.
Lead researcher Zhou-Feng Chen said the fact that a gene had been identified for itching that was unrelated to pain offered hope a specific treatment could be developed.
"It suggests that drugs can be used to suppress the itch sensation without affecting the pain sensation.
"And because pain can be an important protective cue that warns of danger, it may be a distinct advantage to have an anti-itch medication that doesn't compromise our pain-sensing capability."