Epsom salt has been used to treat constipation, insomnia, and back pain. Epsom salt can also be referred to as magnesium sulfate heptahydrate. The reason why epsom salt helps with back pain is that it contains magnesium and magnesium is an important mineral in our spines. Some of the benefits of epsom salt is that it helps to reduce swelling and inflammation, it helps to relax your muscles, and it balances your electrolytes.