the below 2 links have a good explanation down the page on how they both work along with alternatives like Alli which prevents some fats from being absorbed and therefore excreted along with toxins bound to it. you can take without food but you'll see why it makes sense (and is recommended and on the label when you get from pharmacy) to take with food.
www.biotoxinjourney.com/binders-2/"On a molecular level, Cholestyramine (CSM) and Welchol are long polystyrene chain molecules with side groups of positively charged nitrogen – called quaternary ammonium. It is the shape and size of the positive charges on CSM and Welchol that allow them to latch onto the negatively charged Biotoxins. The bound biotoxins are then held captive in the gastrointestinal track and are excreted in stool."
www.gordonmedical.com/unravelling-complex-chronic-illness/mold-and-mycotoxins-often-overlooked-factors-in-chronic-lyme-disease/"Mycotoxins are generally stored intracellularly. For the toxins to be excreted in the urine, they have to leave the cell. In some of the sickest mold patients, if the mycotoxins are sequestered inside the cells, the level of mycotoxins in the urine may be very low and thus the test results may be negative. While the molds themselves live outside the cell, mycotoxins are intracellular poisons and must be released to be excreted from the body. Mycotoxins are lipophilic; that is, attracted to fat. One must
open the detoxification pathways and facilitate the body’s ability to release the stored toxins. Prior to performing the urinary mycotoxin panel, the practitioner must ensure that the patient can detoxify in order to optimize the results."