CRTH2 (Chemoattractant Receptor Homologous Molecule Expressed on Th2 cells), also known as DP2, is a member of the G protein-coupled receptor family, consisting of seven transmembrane domains. CRTH2 is primarily located on the surface of eosinophils, Th2 cells, and mast cells, participating in the regulation of inflammatory and allergic responses. It activates downstream signaling pathways, such as cAMP and MAPK, by binding to prostaglandin D2 (PGD2), influencing cell migration, cytokine production, and immune cell activation. The expression of CRTH2 is specific in different tissues and cells, and mutations or dysregulation in its gene expression are associated with the occurrence and development of asthma, allergic rhinitis, and other inflammation-related diseases.