I know this have happened to a couple of other posters here. It might be the Iodine (in that case I dont know what causes it), but it also might be the potassium in the Iodine you are taking.
This leads us to salt; as potassium and salt are needed in right proportions for the kidneys and the rest of the body.
Drinking a lot of water combined with Saunas would make my body crave for salt, big time, just to stay properly hydrated.
Tried different kinds of salt, dosages etc.? -it is needed for the halide detox, too.