I suspect that the reason this happens is that bile which is highly alkaline kills off the candida. Bile is what keeps the small intestine free of bacterial/fungal overgrowth. However bile is normally absorbed at the end of the small instestine, before it gets a chance to enter the colon. However in a Liver Flush so much bile is released that some inevitably reaches the colon where it causes the classic "stinging" sensation and kills some of the candida.