Magnesium is an important electrolyte that improves and maintains numerous body functions. But while it is not easily absorbed through the stomach, it is easily absorbed through the skin.

Suggested health benefits from proper magnesium levels, as listed on the web site of the Epsom Salt Industry Council, can include:

Improved heart and circulatory health, reducing irregular heartbeats, preventing hardening of the arteries, reducing blood clots and lowering blood pressure.
Improved ability for the body to use insulin, reducing the incidence or severity of diabetes.
Flushed toxins and heavy metals from the cells, easing muscle pain and helping the body to eliminate harmful substances.
Improved nerve function by electrolyte regulation. Also, calcium is the main conductor for electrical current in the body, and magnesium is necessary to maintain proper calcium levels in the blood.
Relieved stress. Excess adrenaline and stress are believed to drain magnesium, a natural stress reliever, from the body. Magnesium is necessary for the body to bind adequate amounts of serotonin, a mood-elevating chemical within the brain that creates a feeling of well being and relaxation.
Reduced inflammation to relieve pain and muscle cramps.
Improved oxygen use.
Improved absorption of nutrients.
Improved formation of joint proteins, brain tissue and mucin proteins.
Prevention or easing of migraine headaches.

All this from a bath!!!