Magnesium can't be absorbed through the skin, can it?
Yes, it can. A randomised, placebo-controlled human trial conducted at the University of Hertfordshire and published in PLOS One found that two weeks of transdermal magnesium application produced a clinically relevant rise in serum magnesium versus placebo, with statistically significant absorption observed in non-athletic participants. Transdermal delivery bypasses the gastrointestinal tract entirely.
Kass L et al., PLOS One, 2017 (RCT, University of Hertfordshire) View source →