Epsom salt is magnesium sulfate, a mineral compound with two main uses. A warm bath soak can help relax tight muscles after exercise and ease everyday tension. When swallowed, it works as a strong, fast acting laxative for occasional constipation. It is not meant to top off low magnesium levels the way daily pills do.
For a bath, dissolve one to two cups in warm water and soak for 15 to 30 minutes. For constipation relief, dissolve the dose in water and drink it on an empty stomach. A bowel movement typically follows within 30 minutes to 6 hours. Limit oral use to short term relief only.
Avoid oral magnesium sulfate if you have kidney disease. Pregnant or nursing women should check with a professional before use. The laxative effect can cause dehydration and excessive fluid loss. Certain prescription drugs may interact, so review medication warnings carefully.