What is a wheal characterized by?

A wheal is characterized by being an itchy, swollen lesion that often appears as a raised area on the skin. Wheals are typically caused by allergic reactions or irritations and are a common feature in conditions like hives. The defining characteristic is their transient nature; they can develop quickly and may fade away just as quickly. This presentation works well for identifying wheals, distinguishing them from other skin lesions.

In contrast, the other options describe different types of skin lesions. A solid mass larger than 1 cm describes a tumor or nodule, which is not associated with the itchiness and evanescent nature of a wheal. A flat, colored spot refers to a macule or patch, which lacks the raised and swollen characteristics of a wheal. Lastly, a clear fluid-filled blister denotes a vesicle, which is entirely different in structure and appearance from a wheal, as it contains fluid rather than being swollen from inflammation or allergic response.