One reason that people are sensitive to probiotics is that it breaks the cell wall of the candida and releases mercury, which the probiotics then can potentially methylate. I know I still have a lot of mercury in my gut (from swallowing mercury on 3 occasions, and from my old type I and type II fillings, and from all the failed DMPS/DMSA treatments which only got a little out and circulated it around my body and nearly killed me), which is why I take enteric coated probiotics, which make it through the acid stomach environment and release in the small intestine.