I am just begining to explore the world of colonics/enemas. Personally I think that a lot of the bad reactions people get are because they are so toxic and these tools are so powerful. My impression is that often so much crud can be removed that the peristalsis is affected. People get constipated and disillusioned. They don't see that the reason they got constipated was because they were so toxic in the first place!
Personally I'm not a big fan of Bentonite, so I just take Psyllium on its own. It can cause leaky gut for those with candida - again because it is so powerful. It can rip candida off the gut wall leaving a bit of a mess behind. Some people do well on it, others don't.
I don't use it indiscriminantly any more.
However - I think its a great tool for occasional use - I use it the day after a liver flush. I just went this morning and I got out at least one extra stone because of the psyllium I took yesterday. It can't do much harm if you use it ocassionally. Problems can only arise if you use it every day.
The other thing is make sure you mix it really well - make sure there are no lumps. Psyllium becomes like concrete if it is too concentrated, and rather than cleansing our bowels it will only clog them up further.
Take a large glass of psyllium mix, followed by at least 2 glasses (same size) of water. I make sure I warm all water first so it is body temperature.