I am one of those who can't tolerate iodine in even the most minute quantities, thanks to about a month of using iodine to disinfect water (only on weekends) back in the 1980's. It makes things really awkward socially; if I'm invited out to dinner I have to ask my host to give me unsalted food or to buy a container of non-iodized salt for all their cooking. For example, I have to turn down the family Thanksgiving dinner with my son#3 and his family because it's potluck and I can't ask half a dozen of his wife's relatives to cook with non-iodized salt just for the occasion! At restaurants (most of which do use iodized salt) I have to stick with salad or something like steak cooked without salt. It also means I can't eat any seafood or anything that has been in the ocean, not even salmon which I love. Finally, it means I have to spend a lot of time and assertiveness with the medical establishment to make sure nobody sneaks up on me with betadyne. Fortunately, there are recent new non-iodine dyes that can be used for angiograms. Until the last few years, if I had needed one, I would have just had to drop dead!

The rash I got from using iodine in the water (and still get if I lapse from the above restrictions) consisted of deep lesions (lichen planus) which itched like crazy, took months to heal and left permanent scars.

Iodine for water disinfection is contraindicated for pregnant women, children and anyone with thyroid problems per the Centers for Disease Control. That should be a warning to the rest of us. It's also (per the CDC) not very effective, especially on protozoa such as giardia and cryptosporidium. There are much more effective chemicals (especially chlorine dioxide) that do far less harm. Please, please, don't use iodine!