MRGPRX2 and inflammation: Although the association between mucosal neurogenic inflammation of GERD and cutaneous neurogenic inflammation of CSU as well as those between serum SP levels and both neurogenic inflammations are currently unknown, preferential activation by SP of human skin MCs via MRGPRX2 [21], and the associate over-expression of this receptor on skin MCs in CSU patients [22] may be a potential connection between mucosal neurogenic inflammation and the onset of CSU.