Vesicles are lesions of less than 5 mm that contain (clear) fluid (Fig. 5.1). In order to distinguish vesicles from small papules of solid content, it is sometimes necessary to puncture the top of a vesicle by means of a vaccinostyle (a pointed lancet) or a small needle, to make sure it is fluid-filled. Vesicles are sometimes conspicuous and produce a translucent lesion, which can be round (hemispherical), conical (acuminate), or depressed (umbilicate) (see Fig. 2.11). However, they are often fragile and temporary and can burst and produce weeping, erosions, and crusting, borders of crusts being rounded, fragmented, or polycyclic. Microscopic vesicles may produce clinical aspects appearing as erythematosquamous or papular. Vesicles evolving towards weeping usually indicate a spongiosis from the histopathological point of view; they are typical of eczema (“dermatitis”). Conversely, vesicles evolving towards umbilication and/or necrosis without weeping often reflect a viral cytopathogenic effect, as in infections caused by herpesvirus or zoster/varicella virus (Fig. 5.2). Oblong vesicles found on extremities are characteristic of hand-foot-and-mouth syndrome (Fig. 5.3). A vesicle should not be mistaken with a hidrocystoma (Fig. 5.4), a translucent sudoral cyst, or pseudovesicles of lymphedema (Fig. 5.5).