PEG Avoid all products made with PEG, polyethylene glycol. Laxative Peg-Lyte are among those products. PEG (polyethylene glycol) with electrolyte is used to clean out the intestines before certain bowel exam procedures such as colonoscopy or barium enema X-rays. It is a laxative that works by drawing large amounts of water into the colon. This effect results in watery bowel movements. In 2011, the FDA has named it in the Adverse Event Reporting System (AERS) in connection to neuropsychiatric events with humans.