AD is a complex, multifactorial, cutaneous manifestation of the atopic diathesis. Observations from bone marrow transplantation cases have shown transmission of the disease from atopic donors [30] and indicate that the basic defect is carried in immune and inflammatory cells which infiltrate skin lesions. Mast cells appear to be important in the initiation of inflammatory events and eosinophils may have an important role in perpetuating the response. New evidence suggests that IL-4 may be a crucial factor controlling mast cells as well as IgE production in allergic disease. The significance of the Fc&RII/CD23 in regulating IgE synthesis and its role in Langerhans' cell/antigen interactions in atopic dermatitis represents an intriguing area in need of further study.