Have a hair analysis, there is usually high toxic metals, and low Zinc.
I have often found high lead and copper in the tap water where people have Ulcerative Colitis.
If you have been using cannabis, which is often high in toxic metals, desist.
It will be beneficial to avoid cows milk, gluten-grains and citrus fruits. (See also
Irritable Bowel Syndrome and Section on Allergies).