In the current study, the mast cell number and concentration of inflammatory mediators (TNF-α, IL-6, and IL-8) of bladder homogenates significantly decreased in the CYP + HC group compared with the CYP + NS group, and bladder inflammation also improved significantly, suggesting that the Houttuynia cordata extract had an anti-inflammatory effect in cystitis induced by cyclophosphamide. This evidence concerns the gene IL6 and chronic cystitis.