Urticaria are raised red bumps (welts) or splotches on the skin. They are a type of swelling on the surface of your skin. They happen when your body has an allergic reaction to an allergen, a substance that’s harmless to most people. But can also occur in autoimmune conditions or systemic conditions, if urticaria last for a prolonged period of time, it may be itchy, or you might feel them burning or stinging. They can be as small as a pinprick or as big as a dinner plate. Sometimes, the welts from urticaria join together to form larger areas called plaques. Urticaria tend to fade within 24 hours, although they may be noticeable for several days or longer.