The exact cause of eczema/AD is unknown. The inflammation results from too many reactive inflammatory cells in the skin. Research seeks to find the reason these cells over-react. Patients with eczema, asthma or allergic rhinitis are born with these over-reactive cells. Research suggests that eczema and other similar diseases are genetically determined. It is not contagious - people with eczema cannot give it to someone else. When something triggers them, their cells over-react which causes inflammation.
AD is known to be a familial disease, though the exact way it passes from parents to children is unclear. If one parent has AD, or any of the other atopic diseases (asthma, hay fever), the chances are 30 to 40 percent that the child will have one or more of the conditions. If both parents are atopic, chances are even greater that their child will have it (60 to 70 percent). However, the connection is not an absolute one - as many as 30 percent of the affected patients have no family members with any of these allergic disorders.