ABSTRACT
Edema of the dermis implies accumulation of serum or water between the collagen bundles. Although some degree of edema accompanies every inflammatory process, in some conditions the edema is quite prominent and is one of the key diagnostic fea tures. The distribution of the edema can be superficial, involving predominantly the papillary dermis or it can be deep involving papillary and reticular dermis. When the edema of the papillary dermis is very prominent, the end result is a subepidermal blister. It is important to distinguish histologically the subepidermal blisters formed by separation of the basal membrane such as in bullous pemphigoid, from those entities in which the blister is due to edema of the papillary dermis.
