Epsom Salts

I started CrossFit training this week. It’s amazing and fun and I had difficulty walking for a few days afterwards! So I walked – slowly – to CVS mid-week to buy Epsom salts. My friend asked me if they really work, which made me curious to research how they work. I suspected the salt was just a carrier for some other chemical that gets dissolved in the bathwater.

I thought this would be a quick project, but I got really into the history research! Here’s what I learned.

For those of you inclined to scroll, here’s the layout of this post:

  • What are Epsom salts?
  • How are Epsom salts made?
  • A Brief-ish History of Epsom Salts
  • The Research on Epsom Salts
  • My Conclusions

What are Epsom salts?

Epsom salt is a compound of two naturally occurring chemicals – magnesium and sulfate. Magnesium and sulfate are both chemicals that help your body run smoothly – especially your bones and joints. The idea is that you absorb the magnesium and sulfate through your skin during an Epsom salts bath.

How are Epsom salts made?

The information I found online was really vague, but here is what I was able to figure out/find:

Magnesium and sulfate can both occur in water. The original “epsom spring” is/was in Epsom, England (more on this below). Originally, people used the waters as is; later, they dissolved the spring water to obtain epsom crystals.

According to the EPA, sulfate occurs naturally in our drinking water, but at small doses (high levels of sulfate can be associated with diarrhea. About 3% of US drinking water has the max recommended level of sulfate [the level at which it affects the taste and smell of the water], but sulfate levels are not regulated by the US government).

Magnesium also naturally occurs in drinking water, but at low levels. In fact, there is concern that many or most Americans may be deficient in magnesium, and there’s some push for magnesium to be added in to our drinking water.

So unless you have a naturally occurring spring with high levels of magnesium sulfate, I would venture to guess that most manufacturers today are producing magnesium sulfate in the laboratory and then infusing salts with it. I saw a few references to using Dolomite crystals, which are made up of magnesium and calcium.

If you’re interested in crystal-growing, the easiest thing is to buy some Epsom salts to start with. Dissolve the salt in the hot water and pour it over a rock in a bowl (that’s the surface for your crystals to grow on). As the water evaporates, the salt will re-crystallize. (source)  Alternatively, you can buy a Dolomite rock for crystal growing.

Dolomite crystals. Image courtesy of geology.com

Dolomite crystals. Image courtesy of geology.com

A Brief History of Epsom Salts

“… medicine sent from Heaven.”
– Nehemiah Grew, “On the Bitter Cathertic Salt in the Epsom Water” (1695)

The original “epsom spring” was in Epsom, England. In the early 1600s, the story goes, some cows refused to drink from the spring. The local people decided that the waters must be medicinal and began using it for open sores, and in 1645 Lord Dudley North published a book promoting the benefits of Epsom waters for open sores, skin conditions and “melancholy”.

Epsom, England is now known for women cheering at the local Derby. Image courtesy of Zimbio.

Epsom, England is now known for women cheering at the local Derby. Image courtesy of Zimbio.

Epsom quickly became a major tourist draw as hundreds – or even thousands, by some accounts – traveled to use the medicinal waters. In 1695, Nehemiah Grew, a physician and member of the Royal Society, published a treatise on Epsom salts. Dr. Grew may have been the first to extract Epsom salts from the water, and he recommended it for a wide array of maladies, including heartburn, poor appetite, colic, diabetes, jaundice, vertigo and many other conditions. He would flavor it with mace, which is still used today as an anesthetic.

By the early 1700s, the external use of epsom salts and waters was established in the “regular” medical profession. (“Regular medicine” was the term for what we now think of as “Western medicine”.) Retailers would boil Epsom water to get the salt crystals. Physicians would prescribe the salts along with instructions for how much water to dissolve them in. Gauze would be soaked in this solution of dissolved Epsom salts and would be applied for twenty-four hours to the affected skin, or patients would drink the solution. Around 1715, subcutaneous – meaning injected under the skin – application of Epsom salts was slowly came into popularity. Applied subcutaneously, Epsom salts were meant to be an anesthetic, relieving pain.

Still in the early 1700s, a Dr. Hoy figured out how to use sea salt to manufacture Epsom salt crystals, driving down prices and raising accusations of bogus imitation medicine.

The Epsom spring remained popular until the mid-1700s, when sea bathing became the newest health fad. Obviously, Epsom salts survived the ages despite the incoming trends.

Sources: Colonel R. D. Rudolf, “The Use of Epsom Salts, Historically Considered” Canadian Medical Association Journal (1917); A. C. Wootton, Chronicles of pharmacy, Volume 1 (1910).

The Research: Do Epsom Salts Really Work?

At first, this question seemed to lead to a lot of dead ends. I couldn’t find any published studies – I found one study that has never been published where the researchers did find increased blood and urine levels of magnesium and sulfate in subjects who took Epsom baths. But I couldn’t find any research on whether absorbing magnesium sulfate is beneficial, or if it needs to be ingested for our bodies to use it.

Since I’ve been seeing a lot in the blogosphere recently about our bodies absorbing chemicals through skin (ie, from using deodorant), I was really bothered by this. Someone had to have looked into it! So I kept looking, and I found a study published in the European Journal for Neutraceutical Research that looked at cellular increases of magnesium using some “magnesium products” (not Epsom salts, but still based on skin absorption). Not only did this study find increased levels of magnesium, but the researchers claim that skin absorpotion might be better than digesting a supplement because the digestion process destroys some of the supplement. The study looked at a really, really small group of people, so it’s hard to say whether the results are really valid. I also can’t be sure that the results apply to Epsom salts.

My Conclusions: Do Epsom Salts Really Work?

The answer is, unfortunately, that I really don’t know. Obviously I’m not a doctor and you shouldn’t take my advice anyway!

It’s honestly hard to say whether we can go on “historical precedent” or anecdotal evidence here. Yes, a lot of people have used Epsom salts for a long time. Hypothetically, if they did nothing for us, we’d have dropped it completely long ago. But human history doesn’t seem to go that way. It’s not so much that we’re good at tricking ourselves as that our bodies do respond to what we expect to feel.

Do Epsom salt baths hurt you? No (unless you use way too much Epsom salts in your bath – follow the package instructions!).

Has it been scientifically proven that they help you? Not really.

So – my conclusion? We need more research. And I would make the argument that it’s worthwhile research. Anything that people are using as a medical therapy should be seriously researched and understood, and it seems that we would additionally benefit from better understanding the ways that our bodies absorb chemicals and nutrients.



  1. I didn’t know any of the background on Epsom salts and of all my random musings, I hadn’t wondered about them but found it interesting. My personal experience has been that they do seem to soothe sore muscles fairly well when I use them in the bath and I always have some on hand.

    1. I’m glad you enjoyed it :-). I tried them for the first time this week in years and I couldn’t decide if they helped or not. But I think that’s because it was my shoulderblades that needed it, and my bathtub isn’t well-shaped for the back/shoulders. I’ll probably try an Epsom salts bath the same day as my next CrossFit class and see how that feels.

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