Magnesium oil may be one of the most important supplements you’ll ever learn about. It’s relatively new, so the word hasn’t gotten out yet – but it will. Magnesium oil is not swallowed, but is applied to the skin, allowing magnesium to be absorbed transdermally. To understand the importance of magnesium oil, you must first understand why magnesium deficiency may be one of the greatest health crises of our age.