I certainly had more gas when I began VSL#3 DS (Double strength, twice the concentration of bacteria as VSL#3). I also noticed and continue to notice that the smell of my stool is different. My initial gas was a bit more odorrific but after a couple weeks (I don't remember exactly, it has been a while), the gas diminished significantly and what gas I would have had minimal odor. The stool still has a different smell than it did previously and I account that to the successful altering of the bacterial flora in my lower GI tract. Initially, I was also taking the probiotic with quite a bit of yogurt. I have cut down on the quantity of yogurt that I take it with and that seems to help lessen the amount of gas/bloating. There are a number of prior posts on this topic if you search the database. I know from participating in those posts that many people do experience increased gas and bloating with the beginning of VSL#3. The makers of VSL#3 recommend starting with smaller amount of the packet and working your way up, however, they also recommend that a higher dosage is taken during active UC. The reasoning being that you are altering the colonation of bacterial flora in your GI tract and need to increase the supply of this bacteria if your bowels are quickly emptying and getting rid of that supply. The studies that have been done on VSL#3 supporting its effectiveness for UC had individuals taking pretty large quantities. Many of the studies were using daily dosages of 4 packets of VSL#3 DS which would be the equivalent to 8 packets of VSL#3 regular strength. This is quite a bit and can obviously get very expensive very quickly. VSL shouldn't cause bleeding...that being said, if your UC is currently uncontrolled and the VSL is increasing gas and leading to more bm's, the resulting activity will seem like more active UC. I would consider increasing the dose slowly until you start to see some improvements in your symptoms. It will likely take a couple weeks but if it works for you, you'll be very happy.