A common intestinal parasite that remains undetected are fluke worms. You may feel them move about your liver if you are on a parasite cleanse-- but otherwise, they just lay in there like slugs--sucking up nutrients and eating liver tissue, etc. A Liver Flush is the best thing to do right after a period of parasite cleansing, since many parasites will find their way into the liver to escape from the anti- parasite herbs.
Sometimes the only evidence you notice that you are infested with parasites is a bloated stomach and minor digestive issues that we all take for granted.