Bulla

Bulla, or BLEBS, are collections of serous fluid of considerable size, situated immediately beneath the cuticle, and raising it from the true skin. They differ from vesicles only in size; and no very definite line can be drawn between a large vesicle and a small bulla. They usually vary in diameter from a quarter of an inch to two inches. The most familiar examples are the 'blisters' produced on the hands by rowing, or the feet by walking. They are met with occasionally in many diseases of the skin—e.g. eczema, erysipelas, urticaria, scabies, &c.; but in pemphigus and in some forms of hydroa they constitute the chief feature of the disease.