The Nuance

Do Epsom Salt Baths Actually Do Anything?

The murky science behind the age-old ritual

Photo: vicnt/Getty

Every week, the Nuance will go beyond the basics, offering a deep and researched look at the latest science and expert insights on a buzzed-about health topic.

EEpsom salt has been around for centuries; medical texts from the early 1900s refer to it as an “old medicinal friend.” But despite its musty history, Epsom salt is lately enjoying a renaissance. You can’t walk into a spa or pharmacy without bumping into a display case full of these magnesium sulfate crystals, and lifestyle gurus like Gwyneth Paltrow extol the detoxifying benefits of soaking in a tub enriched with them.

Epsom salt takes its name from a wellspring in Surrey, England, that was discovered in the early 1600s. The spring’s saline waters were thought to have healing properties, and people started believing that bathing in its waters could relieve sores and infections. Today, some believe Epsom salt can relieve everything from stress and muscle soreness to arthritis-related joint pain. Proponents also say that by leaching into the body’s cells during a soak, Epsom salt can improve heart and vascular health, lower the incidence and severity of diabetes, flush away toxins and harmful heavy metals, and improve nerve functioning.

“I don’t think it’s true that magnesium can get in through the skin.”

But there isn’t much evidence to support these claims. “You will find some benefits of magnesium given intravenously or orally, but the data on soaking is weak and not conclusive,” says Mark Moyad, MD, director of preventative and alternative medicine at the University of Michigan.

The main scientific tentpole around which many Epsom salt aficionados base their beliefs is an experiment from the University of Birmingham in the UK. Researchers found that people who soaked in magnesium sulfate baths once a day for seven days had increased levels of magnesium in their blood and urine, suggesting that Epsom salt can pass through the skin and into the body’s cells and bloodstream.

If true, this could undergird a variety of medical benefits. Magnesium plays a role in a range of biological processes, from facilitating proper muscle and nerve function to aiding protein synthesis and blood pressure regulation. Studies have found that increasing the body’s levels of magnesium may bolster cognitive function following a brain injury and may also be a treatment for some forms of osteoarthritis — to name just two potential benefits linked with magnesium supplementation. Magnesium sulfate is also employed to treat preeclampsia and eclampsia, as well as some heart arrhythmias, Moyad says.

But a recent research review from Germany failed to find any proof that soaking in Epsom salt offers these benefits. The authors of that study point out that the promising UK research — the one that showed soaking in Epsom salt could increase blood and urine levels of magnesium — was never formally published in a peer-reviewed journal.

Experts who have studied magnesium say they’re likewise dubious of any “transdermal” effects. “I don’t think it’s true that magnesium can get in through the skin,” says Max Brenner, MD, an assistant professor of immunology and inflammation at the Feinstein Institute for Medical Research. “Even when people have magnesium deficiency, which can cause mucosal problems, the treatment is oral administration of magnesium — not local administration.”

Brenner explains that human skin is made of fat molecules, while salts are water soluble. Without diving too deep into the chemistry, this makes it highly unlikely that Epsom salt could breach the skin’s barriers during a bath.

No one disputes the idea that soaking quietly in a bath will have some calming, stress-lowering benefits.

Brenner’s own research has also shown that — at least for animals suffering from autoimmune forms of arthritis — increasing magnesium intakes isn’t necessarily a good thing. “Our hypothesis was that magnesium in the diet would improve arthritis symptoms, but we found the opposite,” he says. There are also case reports of people suffering severe liver damage after overingesting magnesium.

“There don’t seem to be strong evidence-based studies to support Epsom salt’s use,” says Rob Danoff, DO, a family medicine physician at Aria Health in Philadelphia, Pennsylvania. “However, I can tell you anecdotally that people do seem to feel better in certain circumstances after using them.”

There is some research suggesting that heat applications — like a warm bath — following exercise can reduce muscle soreness. Likewise, some studies have found “floating” in salt-dense water may reduce muscle aches and pains. And no one disputes the idea that soaking quietly in a bath will have some calming, stress-lowering benefits. But crediting Epsom salt and its ability to penetrate the skin appears to be misplaced, especially when you get into talk about stripping away toxins and lowering diabetes risks.

“But I do recommend that people try Epsom salt, especially seniors who have foot discomfort conditions,” Danoff says. “As long as something will not hurt them, it’s worth a try.”

Danoff points out that Epsom salt has been around for so long that, if it was harmful, we’d know about it. And considering how inexpensive it is, there’s not much to lose in adding an Epsom salt soak to your wellness routine.

I write about health and science. I live in Detroit with my wife and kids. I’m trying to learn German, but my progress so far is nicht gut.

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