The skin creates quite a barrier to things moving into the body.

I don't believe the "oil" form is very useful therefore. It has no carrier, to carry the magnesium thru the skin.

The Morton's lotion however, does go into the skin and the mag goes with it. My blood pressure readings prove that, by decreasing when I use it.

The special compounded creams for pain relief given by doctors and made at compounding pharmacies, use a special transdermal gel that carries the drugs thru the skin barrier.
I bought some of this at a compounding pharmacy for our late cat Oreo who was impossible to pill... for her prednisolone chemo treatments. I mixed her dose into a smidge of the transdermal vehicle, and rubbed it into her ear and it worked like a charm. I had to wear gloves though so it wouldn't get into me.

The Morton's is only $5.95 for 8 oz.... not expensive at all for what you get in return.

You can do what you like, though, but it seems like alot of effort when a product is available that is much better than a concentrated magnesium aqueous solution.