Interstitial cystitis (IC) is a chronic inflammatory condition of the bladder with ulcerative and non-ulcerative subtypes. There has been no specific cause identified. One theory of IC though involves urinary toxins seeping in to the wall of the bladder triggering a release of histamine leading to tissue damage and nerve pain. Damage may also occur to the bladder wall if pressure builds up causing bladder distension.
My recommendations for IC would be to focus on the adrenal glands first and to strengthen the bladder wall. The reason to focus on the adrenals is two part. Chronic inflammatory conditions in the body often result from adrenal dysfunction. Properly functioning adrenal glands produce sufficient levels of anti-inflammatory corticosteroids to keep inflammation down. The adrenals also release epinephrine, the body's own natural antihistamine. Schisandra berry and nettle leaf would both be good choices for supporting the adrenals. Both of these herbs also supply nutrients needed to strengthen the tissues. In particular vitamin C, bioflavonoids, and silica. Nettle leaf also provides the flavonoid quercetin, which is a natural antihistamine. This is how nettle leaf works for allergies, by both supporting the adrenals and due to its antihistamine quercetin. Watercress is also a good choice as well as it also provides nutrients to help stabilize tissues and it is very rich in quercetin.
Another option that may help is supplementing with magnesium malate. Magnesium works as a calcium channel blocker, which helps to relax the smooth muscle of the urethra. This will help prevent a pressure build up that can damage the bladder wall. Recommended dose is 300mg twice to three times daily.