CYP‐induced cystitis is often characterized by decreased bladder compliance, increased urination frequency, bladder epithelial injury, apoptosis of bladder epithelial cells and inflammatory cells, submucosal hemorrhage, inflammatory cell infiltration, significantly upregulated inflammatory factors (especially important inflammatory factors of IL‐1β, IL‐6 and IL‐18), apoptosis‐related proteins and oxidative stress‐related substances in bladder tissue [15, 22, 23, 33, 34, 35, 36]. Here, IL18 is linked to chronic cystitis.