I think the only side effect of “Indigo naturalis” for me is “itchy anus” as I wrote before.
A friend of mine who takes a herbal medicine that is not “Indigo naturalis” every day also said that he has similar symptoms, so I think that these symptoms are not unique to “Indigo naturalis”.
Also, although it is not a side effect, when my ulcerative colitis symptoms were getting better, I sometimes had a feeling of constipation and a sluggish stomach. This is probably similar to the feeling of constipation caused by the fact that for about two years, the bowels were not able to hold stool for a certain period of time to absorb nutrients and water, and the bowels were defecated immediately.
All of these symptoms were welcome if the ulcerative colitis would be relieved.