When the body encounters an allergen, the immune system will produce a series of reactions; immune cells will produce a large amount of specific immunoglobulin (Specific IgE, referred to as IgE). When mast cells encounter this IgE and receive specific stimulation, they will release inflammatory substances such as histamine, prostaglandin, and leukotriene. These substances can cause allergic symptoms: such as skin rash, redness and swelling, asthma, etc. If the allergic reaction is severe, the trachea may swell, causing difficulty in breathing and life-threatening.