The gene which causes dry, scaly skin and predisposes individuals to eczema has been identified for the first time in a major new study which was led by two Irish doctors.
The findings, being published today, are regarded as hugely significant as the first steps towards finding a cure for any condition lie in identifying its cause.
The study was led by Dr Alan Irvine, a consultant paediatric dermatologist at Our Lady's Hospital for Sick Children in Crumlin, Dublin, and Prof Irwin McLean, a geneticist at the University of Dundee in Scotland.
Dr Irvine is from Enniskillen and Prof McLean is originally from Ballymoney, Co Antrim.
Dr Irvine said the research had identified the fact that people who had mutations in the gene that produces a protein called filaggrin, which is normally found in large quantities in the outermost layers of the skin, were likely to develop eczema.
Two-thirds of Irish children with eczema examined carried one or more filaggrin mutations.
Filaggrin is essential in the formation of a protective layer at the surface of the skin.
The study found that about one in 10 Europeans have mutations in the gene that produces filaggrin, switching off its production, causing scaly skin.
About 400,000 people in the Republic only produce half the filaggrin needed for healthy skin and about 8,000 have no filaggrin at all in the skin.
These would have the most severe form of eczema, which can be life-altering.
The research prompted follow-up studies in the Republic, Scotland and Denmark which found that common mutations in the filaggrin gene are also a major predisposing factor in the development of asthma.
"Nobody has known the cause of eczema. This is the first eczema gene to have been identified.
"We are thrilled. It is a genuine breakthrough. Whether it leads to treatment is another thing," Dr Irvine said before thanking families who had participated in the research.
Jeannette Brazel, chairperson of the Irish Eczema Society, said it was a very important discovery.
"I think it's really very exciting. Who knows where it will lead now," she said.
The study is being published in the journal Nature Genetics today.