I've had the same problems with minerals.
I can handle trace minerals ok, but those that are dosed in hundreds of milligrams (Mg, K, Ca...) tend to give me problems. The worst for me is Magnesium, in any form, transdermal included.
I ended up buying a good trace mineral supplement (such as
PicMins by Thorne) and then I experimented with single supplements of Mg, K, Ca etc... and I usually avoid iron and iodine.
For hypersensitive people products with tons of ingredients are more likely to cause issues, but it's very hard to know which are the offending ingredients.