Urticaria, also known as hives, is characterized by itchy wheals (swellings) on the skin that can vary in number, size, and shape. Wheals last hours to days and are caused by swelling in the dermis. Symptoms include itching wheals and flare-ups that can be triggered by pressure, cold, heat, sunlight, or physical activity. Angioedema involves swelling under the skin of the face, lips, tongue, or genitals. Different subtypes have distinct triggers and lesions: dermographic urticaria causes linear wheals from skin rubbing; cholinergic urticaria features transient pinpoint wheals from sweating; cold urticaria involves