Urticaria is a limited edema reaction due to reactive dilation and increased permeability of small blood vessels in the skin and mucous membranes, mainly manifested by the sudden onset of pruritic edematous rashes on the skin or mucous membranes, red or pale, with rapid onset and fading, leaving no trace after elimination, commonly known as “rubella”. Allergic reactions (allergic reactions) to urticaria are the most common. Most of them are caused by IgE-mediated type I (tachyphylaxis) reactions, and a few are caused by immune complex-mediated type III reactions. The causative agents (allergens) are exogenous and endogenous. There are two types of non-allergic urticaria: physical and toxic. Physical factors such as heat, cold, sunlight, pressure, chemical substances such as plant and animal toxins such as caterpillars and urticaria, and certain powerful drugs such as codeine, morphine, aspirin, quinine, hydrazin, etc. can act directly on mast cells to release histamine and other chemical mediators to cause non-allergic urticaria due to their pharmacological effects.