The containers of pure ES (magnesium sulfate, U.S.P.) have instructions for use as a saline laxative and no warning on the label. Hulda Clark guided thousands of people through the Liver-Flush program and none of them became seriously ill altho some of them felt unwell from the release of toxins in the bile. Her program and that of several others start with a parasite cleanse then a kidney cleanse or a stone softening to prepare the body for the LFs. I have read that a rare person can have high toxic levels of magnesium so you could search for 'magnesium toxicity'.
There are several LF's which don't use magnesium laxatives - raw egg/avacado is one.