Quick answer
Epsom Salt is magnesium sulfate heptahydrate (not sodium chloride) from Originally from Epsom, Surrey, England; now manufactured worldwide. Extremely bitter.
Key takeaways
- Epsom Salt is magnesium sulfate heptahydrate (not sodium chloride) from Originally from Epsom, Surrey, England; now manufactured worldwide.
- Despite its name, Epsom salt is not actually salt in the culinary sense.
- Epsom salt baths have been used for centuries to soothe sore muscles, reduce inflammation, and promote relaxation.
- Gardeners have used Epsom salt as a plant supplement for decades.
In 1618, a farmer in Epsom, England discovered that his cows refused to drink from a certain mineral spring. The bitter water was found to have healing properties and Epsom became a spa town. The mineral was identified as magnesium sulfate and named after the town.
Formation: First discovered in natural mineral springs in Epsom, England in 1618
What Is Epsom Salt?
Despite its name, Epsom salt is not actually salt in the culinary sense. It is magnesium sulfate heptahydrate (MgSO4·7H2O), a completely different chemical compound from the sodium chloride (NaCl) found in table salt, sea salt, and other culinary salts. Epsom salt dissolves in water and looks similar to regular salt crystals, but it has a distinctly bitter taste that makes it unsuitable for food. Its primary uses are therapeutic (bath soaks), horticultural (plant fertilizer), and occasionally medical (saline laxative).
Epsom Salt Bath Benefits
Epsom salt baths have been used for centuries to soothe sore muscles, reduce inflammation, and promote relaxation. To prepare an Epsom salt bath, dissolve 2 cups in a standard bathtub of warm water and soak for 15-20 minutes. The theory is that magnesium absorbs through the skin, helping to relax muscles and reduce cortisol levels. While peer-reviewed evidence is limited, a 2004 study from the University of Birmingham showed that blood magnesium levels did increase after Epsom salt baths. Athletes, people with arthritis, and those with fibromyalgia commonly report benefits.
Epsom Salt in the Garden
Gardeners have used Epsom salt as a plant supplement for decades. Magnesium is a central component of chlorophyll, the molecule that allows plants to photosynthesize. Sulfur helps with protein production and enzyme activity. Plants that benefit most include tomatoes (prevents blossom end rot when caused by magnesium deficiency), peppers, roses, and leafy greens. Apply by dissolving 1-2 tablespoons per gallon of water and using as a foliar spray or soil drench monthly during the growing season. Do not overuse, as excess magnesium can interfere with calcium uptake.
Mineral Profile
Composition per 100g for epsom salt. Values vary by harvest location and depth.
| Mineral | Content (g/100g) |
|---|---|
| magnesium | 9.8 |
| sulfur | 13 |
| oxygen | 71 |
| sodium | 0 |
| chloride | 0 |
| Trace minerals | 3+ |
Best Uses for Epsom Salt
Recommended for
- Bath soaks for muscle relief
- Garden fertilizer
- Foot soaks
- Beauty treatments
- Constipation relief (medical grade only)
Not ideal for
- Cooking
- Food seasoning
- Any culinary application
Chef's tip: Epsom salt is NOT a culinary salt. It is magnesium sulfate, not sodium chloride. Never use it as a food seasoning substitute.
Quick Facts
| Origin | Originally from Epsom, Surrey, England; now manufactured worldwide |
| Color | White, translucent crystals |
| Type | Magnesium sulfate heptahydrate (not sodium chloride) |
| Harvest method | Synthesized from magnesium, sulfur, and oxygen or mined from natural deposits |
| Grain sizes | Fine, Medium crystals, Coarse crystals |
| Price range | $1-5 per pound |
Health note: Widely used in bath soaks for muscle soreness. Magnesium can be absorbed through the skin. Medical-grade Epsom salt is used as a saline laxative. Always check that the product is USP grade if using medicinally.
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