The blood levels of mercury aren't high if someone is conuously going through chelation cycles. In fact blood mercury levels rise during chelation, so taking iodine supplements just during on days in the chelation cycle is probably not a good idea. I guess there is no easy answer to all of this. As I said before though, iodine is very antifungal, so a reaction to iodine supplementation is likely due to massive candida die off.