Z-3578 is a small molecule antagonist targeting the MrgX2 (Mas-related G protein-coupled receptor X2) with notable anti-pseudoallergic properties, exhibiting a KD value of 729 nM. It effectively inhibits mast cell degranulation induced by substance P (SP) and C48/80, with IC50 values of 4.90 µM and 6.18 µM, respectively, suppresses the release of β-hexosaminidase, and significantly reduces the release of histamine and TNF-α, as well as intracellular calcium flux. Additionally, in a mouse pseudoallergy model, Z-3578 significantly alleviates foot swelling, dye leakage, and reduces serum histamine levels, indicating a strong in vivo anti-allergic effect. Z-3578 presents as a promising lead compound in the field of anti-allergic treatments, particularly for pseudoallergic reactions.