SCOTS scientists have helped crack the mystery of why some children develop peanut allergies without ever eating a single nut.

The team found that "peanut dust" is floating around a third of UK homes. If the microscopic particles of peanut come into contact with a youngster who has a common skin condition such as eczema, there is an 85 per cent chance they will develop potentially fatal peanut allergy.

The peanut dust causes this effect because it is small enough to enter the child's system through broken skin. Quantities as low as a millionth of a gram of peanut can enter the body through cut or scratched skin.

Researchers at Dundee University were part of the team that found peanut dust even in homes where no-one ate the snack. The academics recommend that parents should cover affected skin in plenty of moisturiser and that extra care should be taken to clean surfaces of dust.

The research, which involved Dundee and Manchester Universities as well as King's College, London, involved vacuuming sofas in the homes of 577 UK babies less than a year old, and testing the amount of peanut present in the dust.

Almost 200 of the homes were found to contain peanut dust. Twenty youngsters developed a peanut allergy, 17 of whom had a skin condition.

Dr Helen Brough, from King's College, said: "Peanut found in dust could penetrate disrupted skin and lead to the child developing an allergy, with an 80 per cent chance that they won't outgrow it."