Blisters are accumulation of fluid lying within or below the epidermis. Only the common conditions will be discussed below. The diagnosis of blistering diseases can sometimes be aided by physical findings.
Subepidermal blister occurs between the dermis and the epidermis.
It contains thick wall and may contain blood. Intraepidermal or subcorneal blister usually has very thin roof. Intact blisters may not be easily detected but leaving erosions only. Palm and sole blisters usually remain intact because of the thick stratum corneum. Grouped vesicles along a dermatome is characteristic of herpes infection.