Which of the following terms describes a localized area of swelling on the skin?

The term that describes a localized area of swelling on the skin is "wheal." A wheal is characterized by a raised, often itchy area of skin that is typically the result of an allergic reaction or skin condition. It is usually temporary, reacting quickly to stimuli such as allergens or irritants, and can appear as welts or hives.

Other terms provided relate to different skin characteristics. For instance, a papule is a small, raised bump on the skin that is not fluid-filled, while a patch refers to a flat area of discoloration on the skin. A lesion is a broader term that encompasses any abnormal change in tissue, whether it be on the skin or elsewhere in the body, and does not specifically refer to swelling. Therefore, "wheal" is the most applicable choice to indicate localized swelling.