Epsom salt baths have no strong scientific evidence behind them for tendonitis specifically, but they likely offer some relief through a simpler mechanism than most people assume: warm water. The heat from the soak increases blood flow and relaxes surrounding muscles, both of which can ease tendon pain. The magnesium in Epsom salt, however, almost certainly isn’t absorbing through your skin in meaningful amounts.
That distinction matters because it changes how you think about the remedy. Epsom salt baths aren’t useless for tendon pain, but understanding why they help (and why they don’t) lets you use them at the right time and pair them with treatments that actually speed healing.
What Epsom Salt Can and Can’t Do
The popular claim is that magnesium sulfate dissolves in warm water, absorbs through the skin, reduces inflammation, and relaxes tight tissue around the affected tendon. The problem is that the absorption step has very little scientific support. A review published in the journal Nutrients evaluated the existing evidence on transdermal magnesium and concluded that the idea is “scientifically unsupported.”
The reason is straightforward biology. Your skin’s outermost layer is designed to keep things out. To penetrate it in significant quantities, a substance needs to be fat-soluble. Magnesium in solution is an ion, not a fat-soluble molecule, and its hydrated form is roughly 400 times larger than its dehydrated form. That makes it nearly impossible for magnesium to pass through skin cell membranes on its own. The body normally moves magnesium into cells using specialized transport proteins, but the dead cells in your outer skin layer don’t have functional versions of those transporters.
Hair follicles and sweat glands do allow trace amounts through, but these make up only 0.1% to 1% of your skin’s surface. One study that measured blood electrolyte levels after a two-hour bath at 95°F found no change in magnesium, calcium, or phosphate concentrations. So while the bath feels good, the magnesium in the water is likely just along for the ride.
Why the Warm Water Still Helps
Even without meaningful magnesium absorption, soaking in warm water produces real physiological effects. Warm water immersion causes blood vessels to dilate, increasing their diameter and improving blood flow to submerged tissue. Research in the International Journal of Environmental Research and Public Health found that this vasodilation reduces arterial stiffness, improves oxygenation, and can mimic some of the circulatory benefits of light exercise.
For tendons, increased blood flow matters because tendons have relatively poor blood supply compared to muscles. Boosting circulation to the area delivers more oxygen and nutrients that support tissue repair. Heat also relaxes the muscles surrounding the affected tendon, which reduces the mechanical stress pulling on it. The Mayo Clinic notes that heat may be particularly helpful for ongoing tendon pain (called tendinopathy or tendinosis) because it promotes healing and eases discomfort by relaxing nearby muscles.
There’s one important caveat: timing. Heat increases blood flow, and in the first 48 to 72 hours after a sudden tendon injury, that extra blood flow can worsen swelling. Ice is the better choice during the acute phase. Once the initial inflammation settles, warm soaks become more appropriate.
When Epsom Salt Soaks Make Sense
Epsom salt baths fit best as a comfort measure for chronic or subacute tendon pain, not as a first-line treatment for a fresh injury. If your tendonitis has been lingering for weeks, or if you’ve just finished a physical therapy session and your tendon area feels stiff and achy, a warm soak can provide temporary relief.
The Cleveland Clinic describes Epsom salt baths as a complementary treatment that integrative medical experts commonly recommend alongside other therapies. The key word is “complementary.” A soak at the end of the day can reduce discomfort, but it won’t replace the treatments that actually resolve tendonitis.
If you want to try it, the standard approach is simple: fill a basin or tub with water between 92°F and 100°F, add half to three-quarters of a cup of Epsom salt, and soak for 20 to 30 minutes. For tendonitis in the foot, ankle, or wrist, a smaller basin works fine. For shoulder or knee tendonitis, a full bath may be more practical.
What Actually Treats Tendonitis
Current orthopedic guidelines emphasize active rehabilitation as the cornerstone of tendonitis treatment. A 2025 clinical practice guideline published in the Journal of Orthopaedic and Sports Physical Therapy recommends an individualized exercise program, which may include motor control exercises and resistance training with various loads, as the primary initial treatment to reduce pain and disability. This applies broadly across tendon injuries, not just the rotator cuff the guideline specifically addresses.
The old advice to simply rest an injured tendon has fallen out of favor. Experts now recommend protecting the tendon for one to three days after an acute injury, then gradually reintroducing movement and load. Prolonged rest can lead to muscle weakness and deconditioning, which makes the tendon more vulnerable when you do return to activity. The current approach is called “load management,” and it involves finding the right balance between protecting the tendon and progressively strengthening it.
For pain management at home, acetaminophen and oral anti-inflammatory medications are both supported by clinical evidence for short-term relief. Compression and elevation remain low-risk options that don’t interfere with healing. Taping and acupuncture, when used alongside an exercise program, have some evidence for reducing pain as well.
Who Should Skip Epsom Salt Baths
Most people can use Epsom salt soaks without concern, but the Cleveland Clinic advises against them if you have severe skin inflammation, skin infections, open wounds, or severe burns. If the skin over your injured tendon is broken or irritated, skip the soak and use dry heat instead, like a heating pad or warm towel.
One more note: don’t drink Epsom salt solutions. Some online wellness guides recommend oral Epsom salt for “detoxing,” but this can cause severe diarrhea and dangerous dehydration. There are no studies showing oral Epsom salt is safe or beneficial.
The Bottom Line on Epsom Salt and Tendons
Epsom salt baths are a low-risk way to get the benefits of warm water immersion: better blood flow, muscle relaxation, and temporary pain relief. The magnesium itself almost certainly isn’t reaching your tendon in any meaningful quantity. That doesn’t make the soak pointless, but it does mean a plain warm bath would likely do the same thing. If you enjoy Epsom salt baths and find them soothing, there’s no reason to stop. Just pair them with the treatments that have stronger evidence behind them: gradual, progressive exercise and appropriate pain management.