It can be concluded that the generation process (antigens activating mast cells through signal transduction) can be classified as direct stimulation, complement, coagulation, kallikrein-kinin, and IgE integrated with anaphylatoxin-triggered pathways (S2 Fig); the effect process (activated mast cells releasing effector substances) is mainly composed of small molecules and proteins such as histamine, which is also an important index for the indication of type I hypersensitivity reactions. Here, KLK4 is linked to IgE responsiveness, atopic.