Interstitial cystitis is a painful bladder condition. Experts don't know what causes it. But it may be linked to an allergy, autoimmune condition, injury, an infection (this is often hard to find), or a problem with the bladder wall. Certain treatments may help manage interstitial cystitis and ease pain. Some people find these treatments work well. But others don't find them useful. Medicines can help ease symptoms for some people. You and your doctor can discuss what's best for you.