i remember researching it and it is derived from seaweed that has been commonly consumed by certain populations through history. i did not find any information that these populations experianced a higher rate of ibd. yet, still there is much good evidence that it can cause intestinal inflammation when administered to rats, im not sure how it is administered or what quantity is sufficient. this is in experimental conditions. whther or not this has any effect or influence on the worsening or development of Crohn's in humans, i have not found nor personally experianced any evidence which strongly suggests this. although i would like to say that about two years before getting crohns i had switched from drinking cows milk to all soy milk and i drank alot.
but it was not until i took amoxicillin that i believe i developed crohn's disease, and there is very good evidence for me to believe that not only in scientific literature, but in my own experiance as well as this is when everything about my body started to change.
id be more worried about antibiotics, but they may actually help improve crohns after you have it already, as now pathogens dominate rather then good bacteria. but id also say avoid carageenan if you can otherwise small exposure to it is most likely safe.