Bulla

A bulla is a larger elevation of the epidermis, by a serous or sero-fibrinous effusion, than a vesicle.
The principal diseases in which bullae are found, and their chief features are:

  1. Erysipelas; The bullae of erysipelas are in reality very large vesicles, seated on the inflamed base.
  2. Leprosy; Large bullae, usually solitary, and appearing at intervals.
  3. Pemphigus; Large bullae, solitary, or in crops at intervals.