Epsom salt is safe to drink as long as one follows the dosing instructions, according to Drugs.com. It is not safe, however, for people who have severe stomach pain, a perforated bowel or a bowel obstruction unless they are under guidance of professional medical advice.
When taking Epsom salt orally, Drugs.com recommends dissolving the appropriate amount inside of an eight ounce glass of water. A small amount of lemon juice can be added to improve the flavor. After drinking, one should have a bowel movement anywhere from 30 minutes to six hours later. If a bowel movement hasn't occurred after the set length of time, then one should call the doctor as soon as possible, as it may be a sign of a more serious condition.