What does Epsom salt do? Breaking down the benefits of this popular treatment.

If you've seen your doctor about joint pain or muscle pain, you've probably been told to take an Epsom salt bath. "Epsom salt baths certainly aren't the cure-all they are sometimes advertised to be," says Jesse Bracamonte, MD, DO, a family medicine physician at Mayo Clinic in Arizona, "but I recommend them to some of my patients because they can be helpful in promoting relaxation and relief from muscle tension." 

Beyond its relief and relaxation properties, Epsom salt likely has other health benefits − though it shouldn't be ingested the same ways it used to be (it's considered safe when taken as directed in supplement form, however), and Epsom salt baths should be avoided altogether under some circumstances. 

What is Epsom salt?

Epsom salt is a naturally occurring mineral salt and is a chemical compound made up of magnesium, sulfur and oxygen. While it shares part of its name with table salt, Epsom salt is a completely different compound than the one used to improve flavor in foods − though both share a similar chemical structure. 

Named after the English town where it was first discovered in an underground spring in the early 1600s, Epsom salt has been used for hundreds of years to treat several ailments ranging from constipation to eclampsia, "though most evidence backing up those early claims was only anecdotal," says Bracamonte.

What does Epsom salt do?

Today, the chemical compound is still a popular remedy for a variety of ailments. Research from the U.S. National Research Council Committee on Diet and Health, for instance, shows that "mineral salts are responsible for structural functions involving the skeleton and soft tissues and for regulatory functions including neuromuscular transmission, blood clotting, oxygen transport and enzymatic activity."

Epsom salt specifically, is often taken as a supplement or used in beauty products such as body scrubs, body wash and soothing nerve lotion. It's also sometimes dissolved in water to drink because doing so has been thought to aid digestion, though Bracamonte doesn't recommend ingesting the raw mineral that way. "There are safer and proven laxative products on the market," he says. Besides, "when ingested like that, Epsom salt can cause dehydration and other medical issues," he adds. 

Beyond its more limited use as a supplement and beauty product, Epsom salt is most frequently marketed and recommended as a soaking agent for bath water. 

What are the benefits of soaking in an Epsom salt bath?

Different than a sitz bath, which usually consists of warm water only and is often taken in a very small amount of water targeting a specific area of one's body, Epsom salt baths are intended to be "full-body experiences where Epsom salt is added to warm water," says Solomon David, MD, a colorectal surgeon at NYU Langone Health. Such baths are often used "to relieve muscle aches, tension, stress, and promote overall well-being," he says. "They are not typically targeted for specific conditions but are more generally used as a form of self-care and relaxation." 

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Do Epsom salts really work?

Adam Tenforde, MD, director of running medicine for Mass General Brigham in Boston, Massachusetts, explains that when Epson salt is placed in water, it breaks down and dissolves into magnesium and sulfate, "and this can be absorbed through the skin," he says. "While not well studied," he explains that such absorption can be beneficial in the aforementioned ways and that Epsom salt baths can also be a helpful treatment for migraines and headaches.

Additional research suggests that Epsom salt baths may also reduce swelling and pain related to arthritis and fibromyalgia; and Bracamonte says the mineral can also be useful as a sleep aid, though again, more research is needed. 

Whether some such benefits have been scientifically proven or not, "there are no serious side effects of taking an Epsom salt bath," says Tenforde. "Although it’s not advised post-surgery or for those with skin conditions that have active inflammation, infection or burn injuries."