You might actually find it helps your large intestine. Iodine is needed in the intestinal mucosal cells (and other mucosal tissues throughout the body).
I've been taking Probiotics recently, and they stopped working after a week. All the IBS symptoms came back, and I felt all bound up in the intestines again. After researching intestinal mucosal cells and iodine, I started taking Iodoral again. Within an hour everything relaxed again.