Final answer:
A vesicle, or blister, is a small fluid-filled sac within the epidermis caused by injury, irritation, or infections such as impetigo. Conditions like sunburns or contact dermatitis can also form vesicles, indicating skin damage.
Step-by-step explanation:
A vesicle, commonly referred to as a blister, is a small, fluid-filled sac that forms in the upper layers of the skin, known as the epidermis. Vesicles are typically a result of injury, irritation, or infections. An example of an infection that causes vesicles is impetigo, which leads to the formation of these blisters, pustules, and possibly bullae, particularly around the nose and mouth. Impetigo is often caused by bacteria such as Staphylococcus aureus or Streptococcus pyogenes. Other conditions such as contact dermatitis or severe skin reactions to the sun (sunburns) can also cause vesicles to appear. In the case of sunburns, the appearance of vesicles indicates damage to the skin's epidermal layer. Consequently, these vesicles can be vulnerable to further infections and may heal slowly.