This article on histamine is a very interesting explanation of the importance of balancing water intake, sodium and potassium for your cells, as related to histamine. If the sodium isn't balanced with potassium so that the potassium can pump the sodium into the cells, histamine takes over to do the job.
Be sure to read the full article, as it contains some cautionary information about drinking too much plain water, as well.
I buy this salt. You can read about potassium-rich foods here.
I came across this link a few days ago in my online reading. I can't remember where! But my reading started on Caroline Lunger's Gutsy. In case it was she who linked to the article, I thought I'd give a shout-out to her. Hopefully I can remember where I read it, so that I can give proper credit to the linker.