Periostin, as a matricellular protein and an ECM protein, exerts different roles in tissue development and progression of diseases, including brain injury, ocular diseases, chronic rhinosinusitis, allergic rhinitis, dental diseases, atopic dermatitis, scleroderma, eosinophilic esophagitis, asthma, cardiac diseases, lung diseases, liver diseases, chronic kidney diseases, inflammatory bowel disease, and osteoarthrosis. The gene discussed is POSTN; the disease is allergic rhinitis.