Epsom salts have many traditional uses, including farming, beauty products, and even soothing sore muscles. Magnesium sulfate, the active compound in Epsom salts, is also widely used as a laxative. Many people favor using Epsom salts instead of traditional store brand laxatives, however the salts can have potentially hazardous side effects, such as cardiac arrest and loss of consciousness, when consumed in large doses. Consumers who prefer the salts over more mainstream products may want to know if Epsom salt is safe for use as a laxative, but the answer is complicated.
Effects of Magnesium Sulfate
There have been cases of deliberate Epsom salt overdoses that have led to serious side-effects such as vomiting, weakness of limbs, confusion, and deterioration of consciousness. Many of those overdose victims survived with no significant damage, but the cases have raised awareness over the possible harmful effect of Epsom salts, especially when used as a laxative. 
Epsom salts are an approved FDA laxative source, and have been shown to produce results that relieve constipation in 30 minutes to one hour in most cases. One study found that some patients who took epsom salts increased their bowl movements from less than two times a day to over six times a day. The study, however, does take steps to prove that Epsom salts can be a safe and viable choice for use as a laxative when people consume them in the proper doses. 
How Do Epsom Salts Relieve Constipation?
How does it work? A study conducted by the Department of Gastroenterology-Hepatology, Leiden University Medical Centre, found that consumption of magnesium sulphate activates the ileal break, which is a substance in the gut that allows more efficient digestion to occur. Epsom salts have been shown to increase digestion, improve bowl movement and constipation, and cause no serious side-effects when taken in the proper doses. The salts also contain natural ingredients that accelerate and improve digestion, which can also lead to an increase in bowel movements.
The best way to use Epsom salt as a laxative is to stir one to two teaspoons of the salt into an 8-ounce cup of water, and allow the solution to dissolve completely before consuming. Taking an Epsom salts mixture once a day while constipated should help return your bowel movements to normal without any side-effects or damage to your stomach.  
Epsom Salts: The Bottom Line
Epsom salts are becoming an increasingly popular choice for relieving stomach pain and constipation, and while consuming too much of the product can lead to serious and potentially harmful side-effects, recommended dosages are a better choice over laxatives that contain harsh herbal stimulants. Still, many people who have used epsom salts to relieve constipation have attested that the experience was not a gentle one and could produce “unpredictable” results.
-Dr. Edward F. Group III, DC, ND, DACBN, DABFM
- Milne H, Dean P, Hughes M. Deliberate overdose with Epsom salts. BMJ Case Rep. 2009;2009. doi:pii: bcr07.2008.0591. 10.1136/bcr.07.2008.0591. Epub 2009 Apr 20.
- Vanner S, Hookey LC. Timing and frequency of bowel activity in patients ingesting sodium picosulphate/magnesium citrate and adjuvant bisacodyl for colon cleansing before colonoscopy. Can J Gastroenterol. 2011 Dec;25(12):663-6.
- Epsom Salt Council. FAQ.
- Vu MK, Nouwens MA, Biemond I, Lamers CB, Masclee AA. The osmotic laxative magnesium sulphate activates the ileal brake. Aliment Pharmacol Ther. 2000 May;14(5):587-95.