Epsom salt is magnesium sulfate, a mineral compound made of magnesium, sulfur, and oxygen. Despite the name, it’s not related to table salt (sodium chloride) at all. It looks like coarse white crystals, dissolves easily in water, and has been used for centuries as a bath soak, a laxative, and a garden supplement. Its name comes from the town of Epsom in southern England, where the compound was first identified in natural spring water in the early 1600s.
How It Differs From Other Salts
Table salt is pure sodium chloride. Sea salt is also mostly sodium chloride, with trace amounts of other minerals mixed in. Epsom salt contains no sodium at all. Its active ingredients are magnesium and sulfate, which is why it behaves so differently from the salt in your kitchen. You wouldn’t season food with it (it tastes bitter), and you wouldn’t soak in a tub of table salt expecting the same effects.
What Magnesium Does in the Body
Magnesium plays a role in over 300 enzyme systems. It helps regulate muscle contraction, supports nerve signaling, and is essential for converting food into energy. The calcium transport system that controls how muscles contract depends on magnesium being present inside cells. When magnesium levels drop, calcium doesn’t release properly from muscle tissue, which can contribute to cramping and soreness.
Magnesium also helps manage lactate buildup during exercise by supporting glucose and pyruvate metabolism in muscles, blood, and the brain. This is why magnesium deficiency is linked to slower recovery and more pronounced muscle soreness after physical activity. Most adults need 310 to 420 mg of magnesium daily, and many people fall short through diet alone.
Bathing in Epsom Salt
The most popular use of Epsom salt is dissolving one to two cups in a warm bath and soaking for 15 to 20 minutes. People use it for sore muscles, joint stiffness, stress relief, and general relaxation. The warm water itself helps increase blood flow and loosen tight muscles, which accounts for some of the benefit.
The bigger question is whether magnesium actually passes through your skin during a bath. The evidence is thin. A widely cited study claiming that Epsom salt baths raise blood magnesium levels was never published in a peer-reviewed journal. It appeared only on the website of an industry trade group. Meanwhile, controlled research tells a different story. A randomized, placebo-controlled trial testing a magnesium-rich lotion applied three times daily found no meaningful change in blood magnesium levels. Separate military research on a magnesium-containing skin lotion also concluded that magnesium does not absorb through the skin.
This doesn’t mean an Epsom salt bath is useless. Warm water, quiet time, and the ritual of self-care can genuinely reduce stress and ease muscle tension. But the magnesium itself probably isn’t entering your bloodstream in significant amounts.
Use as a Laxative
Epsom salt is FDA-recognized as a saline laxative when dissolved in water and taken orally. It works by drawing water into the intestines, which softens stool and triggers contractions. The standard adult dose is 2 to 6 level teaspoons of powder dissolved in 8 ounces of water, taken as a single dose or split into two doses at least four hours apart. It typically produces a bowel movement within 30 minutes to 6 hours.
This use is considered safe for adults and children 12 and older at recommended doses. For children ages 6 to 11, lower doses apply. It’s not recommended for children under 6. Because it pulls water into the gut, it can cause dehydration if you don’t drink enough fluids alongside it, and it’s meant for occasional use rather than a daily habit.
Skin Care Uses
The coarse crystal texture of Epsom salt makes it a simple physical exfoliant. Rubbing it gently on damp skin can help remove dead skin cells and loosen blackheads. Some people mix it with coconut oil or a gentle cleanser to create a scrub. One thing to watch for: Epsom salt can leave a drying residue on skin if not rinsed off thoroughly, so it’s best followed by moisturizer.
Epsom Salt in the Garden
Gardeners use Epsom salt as a source of magnesium for plants, particularly in soils where magnesium is deficient. Magnesium is the central atom in chlorophyll, so plants that don’t get enough of it develop yellowing leaves and poor fruit production.
For tomatoes, a common recommendation is 1 tablespoon per foot of plant height, applied every two weeks. For roses, the same ratio applies, with an additional half cup scratched into the soil at the base to encourage new cane growth. When planting new rose bushes, soaking the roots in 1 cup of Epsom salt per gallon of water can help with transplant recovery. However, Washington State University notes that Epsom salt only helps when the soil is actually low in magnesium. Adding it to soil that already has adequate levels won’t improve growth and can create nutrient imbalances.
Safety and Risks
Soaking in an Epsom salt bath carries very little risk for most people. The safety concerns center on oral use, where taking too much can raise magnesium levels in the blood to dangerous levels, a condition called hypermagnesemia.
At mildly elevated levels, symptoms include weakness, nausea, dizziness, and confusion. As levels climb higher, reflexes diminish, blood pressure drops, heart rate slows, and vision can blur. At very high concentrations, muscle paralysis and breathing difficulty set in. Severe cases, though rare, can lead to cardiac arrest. People with kidney disease face the highest risk because their kidneys can’t clear excess magnesium efficiently. For healthy adults using Epsom salt as a laxative at recommended doses, toxicity is unlikely, but exceeding the stated amount or using it frequently increases the risk.
Epsom salt baths can also irritate open wounds or broken skin. If you have cuts, rashes, or severe sunburn, it’s worth waiting until the skin has healed before soaking.