Which term refers to an itchy swollen lesion caused by an insect bite or allergic reaction?

The term that describes an itchy swollen lesion caused by an insect bite or allergic reaction is known as a wheal. Wheals are typically raised, swollen areas of skin that are often red and can vary in size. They are caused by the release of histamines in response to an allergen or irritant, leading to increased blood flow and swelling in the affected area. This type of reaction is commonly associated with hives and other allergic responses, making the term particularly relevant in the context of insect bites or allergens.

In contrast, the other terms refer to different skin conditions. A bulla is a larger blister filled with fluid, while a vesicle is a small blister also filled with fluid, but smaller than a bulla. Excoriation refers to a scrape or abrasion of the skin, often resulting from scratching or picking at the skin. These definitions clarify why wheal is the most appropriate term for an itchy swollen lesion resulting from an insect bite or allergic reaction.