Named after a saline spring at Epsom in Surrey, England, Epsom Salts are a naturally occurring pure mineral compound of magnesium and sulfate. 

Epsom salt is a popular remedy for many ailments. People use it to ease health problems, such as muscle soreness and stress. It’s also affordable, easy to use, and harmless when used appropriately. In water, Epsom Salts break down into magnesium and sulfate. The theory is that when you soak in an Epsom Salts bath, these get into your body through your skin. That hasn't been proven, but just soaking in warm water can help relax muscles and loosen stiff joints. Most of the reported benefits of Epsom salt are attributed to its magnesium, a mineral that a lot of people do not get enough of.

It has an appearance like table salt and is dissolved in baths, which is why you may also know it as “bath salt.”