A breath test is being designed to spot early signs of diabetes by detecting the smell of acetone, indicating the accumulation of ketones in the blood.

A breathalyser device that can detect the "sweet smell" of diabetes in children is under development by scientists.

The breath test is designed to spot early signs of an organic chemical with a distinctive aroma that is associated with the disease.

Acetone, often used in solvents such as nail polish remover, belongs to a family of compounds called ketones that accumulate in the blood when insulin levels are low.

Left unchecked, ketone build-up can lead to a dangerous condition called diabetic ketoacidosis (DKA) which occurs when the body becomes too acidic.

One in four children with Type 1, or insulin-dependent, diabetes do not know they have the disease until they become severely ill with DKA.

For more than 200 years, acetone has been known to produce a sweet smell on the breath of diabetes sufferers.

But now new research has shown that small traces of acetone on the breath indicate increased levels of other blood ketones and can act as an early warning of Type 1 diabetes.

Professor Gus Hancock, from Oxford University, said: "Our results have shown that it is realistically possible to use measurements of breath acetone to estimate blood ketones.

"We are working on the development of a small hand held device that would allow the possibility of breath measurements for ketone levels and help to identify children with new diabetes before DKA supervenes. Currently, testing for diabetes requires a blood test which can be traumatic for children."

The scientists collected breath samples from 113 children and teenagers between the ages of seven and 18.

Levels of acetone in the samples were compared with those in the participants' blood capillaries. A significant relationship was observed between higher amounts of acetone in the breath and increased levels of blood ketones, especially one known as beta hydroxybutyrate.

No link was found between breath acetone and blood sugar levels.

Ketones are released when a lack of the hormone insulin means the body cannot use glucose for energy and starts to break down fat instead.

The study appears in the Institute of Physics publication the Journal of Breath Research.