Probably not in any meaningful amount. Despite decades of popular claims, there is no strong scientific evidence that magnesium from Epsom salt (magnesium sulfate) absorbs through your skin in quantities large enough to affect your health. The idea is widespread, but the research behind it is surprisingly thin.
What the Science Actually Shows
The study most often cited to support Epsom salt absorption comes from the University of Birmingham, where 19 people took full-body baths in magnesium sulfate solution for 12 minutes a day over seven days. Blood and urine samples were collected before, during, and after the bathing period. The results reportedly showed some increase in magnesium levels. But here’s the problem: this study was never published in a peer-reviewed scientific journal. It appeared only on the Epsom Salt Council’s commercial website, meaning it was never subjected to the independent scrutiny that separates credible research from marketing material.
A 2017 review published in the journal Nutrients, titled “Myth or Reality: Transdermal Magnesium?”, examined the available evidence and found the quality of studies supporting skin absorption to be seriously lacking. No well-designed, peer-reviewed clinical trial has demonstrated that soaking in Epsom salt raises blood magnesium levels to a degree that would produce therapeutic effects.
Why Skin Makes Absorption Difficult
Your skin’s outermost layer, the stratum corneum, is specifically designed to keep things out. It’s a tightly packed barrier of dead cells and oils that blocks most substances from entering the bloodstream. Charged particles like magnesium and sulfate ions have a particularly hard time crossing this barrier because they’re water-soluble and the stratum corneum is lipid-rich, essentially a wall of fat.
There is one partial exception. Research from 2016 found that hair follicles can serve as a shortcut for magnesium ions, allowing some penetration that bypasses the stratum corneum entirely. The study confirmed that magnesium does cross human skin to some degree, and that the amount depends on concentration and how long the skin is exposed. However, hair follicles make up only a tiny fraction of your total skin surface area, roughly 0.1%. So while this pathway exists, the total volume of magnesium getting through is likely very small.
Why Epsom Salt Baths Still Feel Good
If the magnesium isn’t meaningfully absorbing, why do so many people swear by Epsom salt baths for sore muscles and relaxation? Several things are probably happening at once, none of which require magnesium absorption.
Warm water itself is a well-established way to ease muscle tension and reduce pain. Heat increases blood flow, relaxes tight muscles, and triggers your body’s relaxation response. The buoyancy of water takes pressure off joints. Spending 15 to 20 minutes soaking in a quiet bathroom, away from screens and stress, also has real psychological benefits. The salt in the water increases its density slightly, which can make the bath feel more soothing against your skin. All of these factors can explain the relief people experience without invoking magnesium absorption.
There’s also a strong placebo effect at work. If you believe the bath is delivering therapeutic minerals, you’re more likely to notice any improvement in how you feel and attribute it to the salt.
How to Use Epsom Salt Baths
Even without proven absorption, Epsom salt baths are safe for most people and can be a genuinely relaxing practice. For a full bath, two cups of Epsom salt dissolved in warm water is the commonly recommended amount. Soak for 15 to 20 minutes. For a foot soak, half a cup in a basin of warm water covering your ankles works well, again for about 15 minutes.
Epsom salt can be drying to the skin, so moisturizing afterward is a good idea. Limit soaks to once or twice a week rather than daily to avoid excessive dryness. The salt also acts as a mild exfoliant, which can soften rough skin on the feet.
If You Actually Need More Magnesium
Roughly half of adults in the United States don’t get enough magnesium from their diet. If you’re looking to correct a deficiency, soaking in it isn’t a reliable strategy. Oral magnesium, whether from food or supplements, is the proven route. Foods rich in magnesium include pumpkin seeds, almonds, spinach, black beans, and dark chocolate. Oral supplements are widely available and have well-documented absorption rates, typically between 30% and 50% depending on the form.
People with kidney disease should be particularly cautious around Epsom salt, whether oral or in baths. The kidneys are responsible for clearing excess magnesium from the body, and impaired kidney function can lead to dangerous buildup. Pregnant people and those with heart conditions should also check with a doctor before using Epsom salt in any form beyond a simple soak.
The Bottom Line on Absorption
Some magnesium ions can technically cross the skin barrier, primarily through hair follicles, in amounts that increase with concentration and soak time. But no rigorous, peer-reviewed research has shown this happens at levels that would meaningfully change your blood magnesium or produce the health benefits commonly attributed to Epsom salt baths. The relaxation you feel is real. It’s just more likely coming from the warm water and the quiet time than from the salt itself.