The reason salt had iodine added to it was to correct the diets of people who lived inland and did not get a diet in foods that contain natural occurring trace amounts of iodine, such as:
"Iodine is found in the sea and in soil that has previously been under the sea. Salt water seafood (e.g., sea trout, lobster, haddock, shrimp, and shark), sea vegetables (such as seaweed, including kelp, hijiki, arame, nori, and laver), vegetables grown in iodine containing soil (found on any land that was previously under the sea), and animals grazing on plants growing in iodine rich soil all are good sources. This mineral also enters the food supply through the use of certain disinfectants called iodophors. These are primarily used in the dairy industry, so milk and cheese, for example, contain a good amount of iodine. In addition, some red dyes contain iodine, as do some dough conditioners (look for an iodized conditioner listed in the ingredient section on the bread package). These sources add considerable amounts of iodine to one's diet." http://www.goaskalice.columbia.edu/2234.html
Hence, yes, folks, we can EASILY over due it on iodine in our diets. It is used heavily where we do not need that much of it.
In Granny's case her allergy occurred after using quite a bit of it to purify water. In most cases iodine is not recommended for daily water treatment – as a backup emergency method, yes.
Unless you were AT her Dr. appointments, suffering what she went through I call BS on comments!