IGHE and Allergy: 2021). However, the detailed mechanism is not yet fully elucidated. Allergic reactions can be divided into four types, each of which has a different mechanism. Among them, type I allergy (TIA, IgE-mediated) is the most clinically common (Liu et al. 2016), which is a complex immune response. The combination of IgE and FcεRI on the surface of mast cells (MC) or basophils is the key step, leading to aggregation and crosslinking reactions, which can induce MC or basophils releasing sensitising agents to cause allergy (Pedretti and Peter 2020; Shin et al. 2015).