(Little blisters; Vesiculae)
Definition. Vesicles are pin-point to pea-sized, white, yellow or red, circumscribed elevations of the epidermis containing a serous fluid.
Vesicles arise as such or are secondary to pre-existing papules. Their color depends not only upon their contents which may be clear (from serum) or opaque (from pus, blood or both), but also upon the degree of inflammations present. They tend to appear in groups or aggregations as in eczema, herpes simplex, herpes zoster, dermatitis herpetiformis, or they may be scanty, discrete, isolated or disseminated as in varicella, malaria, sudamen and hydrocystoma. They are generally tense; rounded at the base, if discrete; convex at the top or pitted as in varicella, or flaccid from collapse upon their contents; tend to coalesce and form blebs; are usually single chambered but may be multilocular as in smallpox.
Vesicles are usually of inflammatory origin, as in eczema; however, they may be non-inflammatory, as in sudamen. They may be the chief feature of an eruption and seated in the skin, as in herpes; or they may be secondary and external to other lesions, as at the apex of a papule in eczema. Vesicles are of comparatively short duration. They terminate by spontaneous or accidental rupture and discharge their contents upon the adjacent surface, or they may dry into crusts. They may be transformed into bullae not only by coalescence but also by an increase of size, or become pustules or the seat of ulceration. An eruption of inflammatory vesicles is usually attended with subjective sensations of itching, burning or stinging.
The terms vesicopustule and vesicobullae are used to designate conditions in which pustular and bullous formations are secondary to that of the vesicular.