Scottish scientists have developed an "itchometer" - a device to measure how often children itch while asleep.
The device could help children with eczema
They say the device, which is worn around the arm like a watch, can help children with skin problems.
According to the scientists at the University of Edinburgh, children with eczema and other conditions scratch differently while asleep.
Writing in the Journal of the American Academy of Dermatology, they said the device would help doctors monitor this.
Professor Jonathan Rees's team had already tested the "itchometer" out on 21 children. Of these, 14 had eczema and seven did not.
Using the device , the researchers discovered that the children with eczema had on average 46 minutes less sleep than those without the condition.
In addition, they were at least twice as restless during the night.
The "itchometer" - a type of accelerometer - measures movement. The data can be obtained by plugging the watch-like device into a computer.
Professor Rees said the study showed that the device could be useful.
"Itching is a major symptom of skin disease and remains poorly studied.
"Our research shows that nocturnal scratching and restlessness are more complex than we first thought, with many movements that potentially damage the skin not conforming to
typical scratch movements.
"Accelerometers provide a useful and practical way of assessing scratching at night in the patient's own home and could be used as an objective measure of disease activity, both in clinical trials and in everyday clinical practice."
Matthew Patey, director of the British Skin Foundation which gave money towards the project, said the device would help many people.
"With over 30% of children presenting with paediatric eczema before the age of four and young sufferers and their families having to endure endless sleepless nights, we welcome the introduction of this device for monitoring itch.
"We hope that further studies like Professor Rees's may help lead to a greater understanding of paediatric eczema, alleviate the suffering of so many and pave the wave to an eventual cure for this terrible condition."