"The medical name for eczema is atopic dermatitis, which reflects the immunological nature of the condition. It is more common among children living in cities than those in rural areas. According to the so-called hygiene hypothesis, exposure to infectious agents early in life offers protection against allergic diseases. The more hygienic a child’s environment, the greater the risk." This is an extract from a good article by Jane Brody who writes the Personal Health section for the NY Times. I don't agree with everything, but it's a good starting point.
For full text see: Download Eczema NYT
A good guie to eczema for patients and parents is:
Your Guide to Eczema by Sarah Wakelin which can be ordered from ABE books for ~ $4 (includes shipping)