Hidden Downsides of Magnesium Baths

If you're dealing with sore muscles, stiff joints, fatigue, or itchy skin, sinking into a magnesium sulfate bath can sound like an ideal fix. For years, people have praised Epsom salt baths for their supposed ability to soothe the body and ease musculoskeletal discomfort. The catch is that these baths may also bring unexpected side effects that create new issues.

Magnesium sulfate baths are made by adding a salt composed of magnesium, oxygen, and sulfur to warm bathwater. As the salt dissolves, it leaves behind a magnesium-rich soak meant to relieve aches. Some people believe the mineral can enter the body through the skin during the bath, but that claim remains uncertain. A 2017 review in Nutrients found that while a few studies, including some involving magnesium baths, hinted that this might be possible, the evidence was not strong enough to prove it.

Even so, some people warn that magnesium sulfate baths can trigger muscle problems, nausea, or diarrhea if too much magnesium is absorbed. There is no solid scientific evidence showing this under proper scrutiny. By contrast, people who drink magnesium sulfate solutions to ease constipation may experience those kinds of symptoms, so that approach is best avoided.

Could it soothe the skin, or irritate it?

Even if you decide to try a magnesium sulfate bath despite the possible stomach or muscle issues, the experience may still surprise you in another way. Magnesium sulfate can sometimes cause topical reactions, even if little or none of it is absorbed through the skin.

Some people have reported hives or a rash after bathing in magnesium sulfate. If you want to be cautious, you could test it on a small patch of skin first by mixing a little magnesium sulfate with warm water. It is also wise to avoid this type of bath if you have an open cut or sore.

At the same time, magnesium sulfate does not always irritate the skin. For some people with eczema, it may even be helpful. In an article for HealthCentral, skin disorder specialist Dr. Danielle Dubin said topical magnesium may work in an anti-inflammatory way that helps calm eczema. She also noted that reports of benefit are based largely on personal accounts or on research involving magnesium sulfate in other settings.

Dr. Dubin recommends several practical steps for using magnesium sulfate baths with eczema, including moisturizing afterward, using them only occasionally rather than often, and adjusting the amount of salt depending on how your skin responds. In other words, you may need some trial and error to see how your body reacts.

The warm water may matter most

Overall, bathing with magnesium salts appears to be a relatively safe way to try to soothe tired muscles or help with an eczema flare-up. There are also other ways to reduce eczema flare-ups, such as planning your diet carefully and identifying triggers. Still, a plain warm bath may offer many of the same calming benefits for both body and mind.

Sports medicine expert Dr. Dennis Cardone told Nike that the main benefit of an Epsom salt bath may simply come from the bath itself. He said the advantages seem to be tied entirely to soaking in warm water, which can be relaxing and support mental and emotional well-being. A 2019 review in Sleep Medicine Reviews found that a warm bath or shower before bed can improve sleep quality. Likewise, a 2025 study in Physiological Reports concluded that hot baths or showers after exercise may reduce feelings of muscle fatigue.