i agree with wilson as you will see from my previous comment. also, another symtom of IBS is mucus in the stool. for myself i decided that the food alergy (intolerance) and IBS are not the same thing. The mucus problem (slippery and can't be stopped) might be eliminated by cutting out or down on greasy food.
IBS is supposedly a motility disorder where the contractions of smooth muscle in your intestines are out of sync, causing diarrhea (food moves too quickly), constipation (too slowly), or a combination of both. As far as I know it's a diagnosis of exclusion, which means when all other tests have shown no "organic" disease is present and these relatively mild symptoms persist, they call it IBS. They say symptoms are brought on mostly by stress and food allergies/intolerances. I have a little firsthand experience on the subject, and it's my personal belief that the food allergy aspect is often underemphasized.