What characterizes a vesicle?

A vesicle is characterized by being a small, thin-walled lesion that contains clear fluid. This definition aligns with medical terminology used to describe various forms of skin lesions seen in dermatological conditions. Vesicles can be found in various scenarios, such as viral infections or in cases of allergic contact dermatitis, and they are typically less than 1 centimeter in diameter. Their fluid-filled nature differentiates them from other lesions, such as pustules, which contain pus, or larger lesions like blisters.

Other options provided describe different medical conditions or lesions that do not reflect the characteristics of a vesicle. For example, deep, full-thickness burns refer to severe injuries where all layers of skin are damaged, and pressure ulcers indicate local damage to the skin resulting from pressure and are not fluid-filled lesions. Absence of skin pigment relates to conditions like vitiligo or albinism, which does not correlate with the definition of a vesicle either. Therefore, the correct option distinctly captures the defining features of a vesicle as a specific type of skin lesion.