The cause of interstitial cystitis is listed as unknown. To me, that means FUPO. (fungus until proven otherwise).
I would suggest taking some natural antifungals, such as grapefruit seed extract, coconut oil, oil of oregano, or colloidal silver, or some combination of these.
Almost every disease with an "unknown" cause is the result of mycotoxins, produced by yeast, mold, or fungus. That would include gout, diabetes, copd, sinusitis, arthritis, hypertention, as well as several "cancers".
Let Food Be Your Medicine And Medicine Be Your Food.(Hippocrates)