I want to caution about the use of iodine.

After only a month of using iodine for water disinfection, I broke out in a horrible rash, with deep lesions (lichen planus) that left permanent scars. To this day (25 years later), I cannot tolerate seafood, iodized salt or multi-vitamin/mineral products, nearly all of which contain iodine. The iodized salt is a particular problem--when invited to someone's house for dinner or eating at a restaurant, I have to request specially prepared food (no-salt is the easiest) or stick with salads with oil and vinegar on the side (no house or home-made dressings). If I ever have to have a medical diagnostic test that uses iodine, such as an angiogram--well, I'll just have to die of the undiagnosed ailment! Per several doctors I've consulted, allergies to iodine are not at all unusual. Per the CDC, iodine is to be used for water disinfection only in emergencies and is contraindicated for pregnant women and small children (which should tell you something). It is also ineffective against cryptosporidium, which is becoming more common.

I've posted this information several times on this site, but it seems that in almost every water purification thread, someone always pops out of the woodwork recommending iodine for water purification. Not everyone is sensitive to iodine, but enough people are that it should never be recommended for general use--not just in my own opinion, but in the opinion of a number of medical authorities I've consulted.