We actually sell Waterfall D-Mannose, and although we don't sell it as a cure for interstitial cystitis, some sufferers have given us positive feedback, indicating that it is relieving their symptoms. Primarily D-Mannose is useful for flushing out infections, but it does hook onto the mannose receptors throughout the body. Relief may be (unconfirmed - this is just a guess) caused by the coating effect. When the cell mannose receptors are filled, it prevents anything else from latching on, so could prevent irritation by acids/alkilis etc. More research obviously needs to be done. However, it is very unlikely to cause an increase in interstitial cystitis symptoms, unless the person was infected with both E.coli and, say, Proteous, which, when the E.coli was flushed away might allow the Proteous to multiply more. Worth remembering that Proteous thrives in an alkiline environment too, so potassioum citrate etc does not work to clear it away...