What is a bulla?

A bulla is defined as a large blister that is typically filled with clear, watery fluid. It forms when there is a separation within the layers of the skin, which allows for fluid accumulation between them. The size of a bulla distinguishes it from smaller blisters; it is usually greater than 0.5 centimeters in diameter. Understanding this definition is crucial for accurately identifying skin conditions and their manifestations.

It is important to note that the other options describe different skin features. A small raised area of skin would typically refer to a papule, which is smaller than a bulla. A type of skin rash could encompass a variety of conditions, such as eczema or dermatitis, which do not specifically indicate the fluid-filled aspect of a bulla. Lastly, a benign skin growth might refer to conditions such as seborrheic keratosis or moles, which are entirely different from the characteristics of a bulla. Hence, the selection of the correct definition aligns with its medical classification and description.