What you put on your skin goes directly into your lymphatics and circulation without passing the liver first, as happens when we eat something. And, some chemicals are more permeable across the skin than across the gut. You should not put anything on your skin that you would not eat! Autopsy studies show that mineral oil widely permeates our internal organs and bioaccumulates particularly in the liver and spleen.
Coconut oil is a much better choice because it is not toxic and in fact is healthy for us. It also works very well as a skin moisturizer; it even penetrates the shaft of hair, while mineral oil does not.