In some people, yes it is. Scientists have discovered very recently (in 2006) that half the people who have eczema that can't be tied down to any known cause have a genetic change in one of their genes. They have an altered filaggrin gene, which stops them making a fully functional copy of the filaggrin protein.
This protein forms into long filaments or threads in the outermost layers of the skin. It cross links with keratin filaments to enable the skin to be a strong barrier that can keep out irritants and microorganisms that are all around us in the environment. When the filaggrin gene is mutated, this protein doesn't form properly and it doesn't do its job. The result is skin that is prone to damage and infection ~ and which responds by becoming red and flaky. These are the typical signs of eczema.
About 1 in 20 adults and 1 in 10 children today have eczema. Identifying this gene could lead to new treatments for this condition that can range from being annoying to seriously affecting quality of life.