Written by Raymond Nakamura
Once upon a time (before the Internet), Raymond earned his doctorate studying the hydrodynamics of sand dollars. Nowadays he rents his brain at raymondsbrain.com for writing, cartooning, and thinking, when he is not washing the dishes, walking the dog, or helping his daughter with homework. Follow him on Twitter @raymondsbrain.

epsom salts in bath water don't do much

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Sunday, November 1, 2015 - 8:00am

Ever Wonder About Epsom Salts?

While clearing out my in-laws’ old house, I realized how easy it is for all kinds of junk to accumulate over time. Was a bag of Epsom salts, for example, worth keeping? I'd heard that a warm bath with Epsom salts relieves sore muscles and wondered if it really made a difference. I was plenty sore from moving and removing forty years of stuff, so I thought I’d try it out.

The warm bath was pleasant enough, but I did not notice any particular effects beyond taking a regular bath. Maybe it was just me, so I looked for some evidence of the effectiveness of Epsom salts.

Epsom salt is a singular compound called magnesium sulphate. Back in 1695, Nehemiah Grew patented the name Epsom salts for "bitter purging salts" found in Epsom, England. They are still taken internally as a laxative, but I wanted to know about its usefulness in a bath. Henry Wicker set up the first spa in Epsom in the early seventeenth century after he noticed his cows would not drink the water of a natural spring. The Saltworks web site claims, "An Epsom salt bath is known to ease pain and relieve inflammation, making it beneficial in the treatment of sore muscles, bronchial asthma and migraine headaches." And the Epsom Salt Council site asserts, "Doctors, celebrities, personal trainers, gardening experts and supermodels have all extolled its virtues." Despite the unspecified endorsement of such scientific authorities as celebrities and supermodels, I could not find any evidence that adding Epsom salts to a bath does any good for aches and pains. 

Sites advocating the use of Epsom salt for bathing, seem to assume its effectiveness and then provide some speculations on why it might work, mentioning how Magnesium is an important trace element in the body, playing significant roles in bones and many physiological processes. Apparently, many people might be lacking in Magnesium and adding some to your system must be a good thing. Taking a bath in the stuff doesn't seem like a very efficient strategy because skin does not easily absorb materials. The Epsom Salt Council quotes an unpublished paper by a toxicologist that magnesium levels rose after taking a very hot bath with Epsom Salts, although this study did not control for the effect of taking a normal bath. And the usefulness of increasing magnesium levels in the blood in relation to muscle aches is unclear.

Osmosis involves moving water molecules from one side of a permeable membrane to another. Even if this were happening (and no evidence was shown that it was) the relevance to muscle pain is unclear. You would need a higher concentration than indicated, and if removing fluid were relevant to the problem, then other kinds of salt would also work.

One of my problems with culling things and ideas is that I'm never totally sure about how I feel about them. So if you have any good evidence for the usefulness of Epsom Salt in a bath, by all means, add them to the comments below.

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When I was looking into this

When I was looking into this I found only one inconclusive paper by Rosemary Waring. As a RMT who was a former chemist I simply cannot tell my patients to take an "Epsom salt" bath for the reasons all those other websites you likely found in your research state. Why? Because I can't explain any science behind the claims. So I personally think you get just as much benefit from taking a regular warm/hot bath (hydrotherapeutic effects). An interesting read can be found at the following link (he's a tad controversial I suspect) https://www.painscience.com/articles/epsom-salts.php

Apparently, epsom salt are

Apparently, epsom salt are found in the asteroid belt... http://www.cbc.ca/news/technology/ceres-spots-1.3357463

I have been told for years

I have been told for years that using Epsom salts would be good for you but you’re absolutely right, where is the proof. The heat that is usually in the bath anyways is what really helps relax muscles and ease away pain. A bath is supposed to be relaxing and that should be enough for the stress to melt away. The Saltworks website also is more of a marketplace than a research site, can the info even be trusted? It is like one of those miracle cures from the Wild West, guaranteed to cure everything. I may as well just light a candle and have lots of bubbles. There are some effects that it says it has on plant life, is there any research behind these “facts” to prove them true?

search for hemorrhoids and

search for hemorrhoids and epsom. there seems to be at good deal of opinion supporting its use!

This is very interesting. The

This is very interesting. The only reason I have Epsom salt in my house is because my nurse told me to take a "sit" bath with Epsom salt after I delivered my son "to help with healing." I did and the carton has now been sitting in a cupboard for a decade. I just got back from the gym and saw the carton, read the claims and thought, "ah good it's also for sore muscles." But now as I sit here, in the bath on my phone, looking for evidence, I'm feeling really uncomfortable that the medical community is recommending this product. It seems like a relic from the past that has just held on flying under the radar.

I laughed out loud because I

I laughed out loud because I'm doing the exact same thing. Sitting in an Epson salt bath for the first time researching on my phone for proof it works.

I've had a dozen or so baths

I've had a dozen or so baths with Epson Salt or Magnesium flakes and it has a strong and fast acting effect on me compared to a normal bath. I'm engineer so all for scientific method but even with a sample size this small the magnitude and reliability of the reaction lead me to believe it's almost certainly from the magnesium. The question in my mind is not whether it does something but precisely what it does and how. During/immediately after a bath with magnesium in it I feel very relaxed, sleepy and generally lethargic. I also feel slightly light headed and sometimes nauseous. This feeling gradually declines over about 36 hours or so. I've spoken to a number of others who have similar experiences and see there are many such on the web. Rather than discounting these as psychosomatic which seems highly unlikely to me the focus should be placed on understanding why it has the effect it does, and whether this is in fact good for us who choose to use it.

In my own experience a bath

In my own experience a bath with Epsom salt softens the skin, especially hands calloused from intensive gardening. The identical bath without Epsom salt renders a much less pronounced improvement. My own unintended experiment emerging over a long spring and summer of nightly 20-minute baths. I also found when I put my glasses in the bath they were sparkling clean in contrast to how they emerge without Epsom salt. So it is penetrating and having some effect. I agree with David's note just above: I'd like to know precisely what the less noticeable effects may be.

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