Does anyone have a good understanding of what emulsifiers (carrageenan, soy lecithin, etc.) specifically do to hurt the colon? Every single time I accidentally consume these emulsifiers in something like ice cream for example, it immediately leads to colon and rectum bleeding the next day. I could have had no bleeding for weeks or months and one mistaken consumption of these emulsifiers and I immediately get bleeding, pain and terrible symptoms the next day. What are these emulsifiers specifically doing in the colon and rectum that leads to these painful symptoms?

In general, emulsifiers help dissimilar substances to mix. Think about emulsifiers in salad dressing that allow oil and water to mix (form an emulsion although not dissolving in each other) so they don't separate out so quickly.

There is some evidence that emulsifiers increase mixing in the mucus layer lining the colon. There are bacteria that are beneficial as long as they remain in the foodstream (chime or feces), but if they penetrate the mucus layer and into the intestinal lining, it triggers an immune response, e.g., inflammation. Mouse studies on a couple of emulsifiers (polysorbate 80 and carboxymethylcellulose) showed increases in some bacteria in the lining of the colon.

So basically emulsifiers can cause bacteria to migrate to where they shouldn't be, and trigger inflammation.

Carrageenan is a HUGE problem for me. I used to roll my eyes at people who said to avoid it, but found the same thing after keeping a careful food and symptom diary - I start cramping and bleeding almost overnight if I consume it. Literally. No exaggeration. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5410598/