[burning_hamster]

It is worth noting that these topical applications are quite controversial in the medical literature. The evidence supporting a dermal absorption of magnesium (or other electrolytes) is pretty poor [1]. In that sense: yes, it would be exceedingly difficult to overdose using them.

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5579607/

[ivankra]

Underresearched topic for sure. They do cite studies that show some effects, just not convincing enough. Perhaps the weak effects are because they seem to overindex on serum magnesium levels, which is just not a good marker of magnesium status (unless very deficient). It's largely an intracellular/skeletal element and serum levels are quickly maintained by kidneys within a narrow range. Magnesium RBC is a much better biomarker but it's hard to find any studies that focus on it. Here's one but in a non-mainstream journal: https://ijlbpr.com/uploadfiles/462vol12issue2pp2557-2563.202...

Anectodally, while on B6, I had a period of magnesium intolerance - it was a reliable trigger for my dysautonomia flares. I did have reactions to magnesium chloride spray - tachycardia, blood pressure spike, sometimes headache within ~15 minutes of applying it.

[jaggs]

There's an awful lot of personal susceptibility linked to the use of magnesium I suspect. In other words what's good for one person may not be good for another. For me magnesium in chloride hexahydrate form converted into a magnesium oil spray is great for a lot of things like aches and pains, and even improving sleep patterns. It's also dirt cheap if you make it yourself. Also magnesium citrate is perfect for me to regularize bowel movements. But again, YMMV.