#blister__bulla__bleb  (pathology) an elevation of the skin filled with serous fluid
  supertype:  vesicle__cyst  a small anatomically normal sac or bladderlike structure (especially one containing fluid)
  subtype:  water_blister__waterblister  blister containing a nonpurulent clear watery content
  subtype:  blood_blister__bloodblister  blister containing blood or bloody serum usually caused by an injury

No statement uses or specializes blister; click here to add one.