I am sure that one of the moderators will explain this better, but if I understand things right Iodine displaces substances that are toxic in our bodies. For example if you drink a Mountain Dew or two everyday for years, you are consuming bromated vegetable oil. Iodine supplementation will displace the bromide. It will eventually be flushed from your body, but may cause detox symptoms until it is gone. Iodine can also act as an antibacterial agent, an anti-inflammatory and possibly be anti-viral as the blood goes through the thyroid gland. Anytime a stored toxin is loosened there is a potential for a detox reaction. I know this explanation is oversimplified, but perhaps it will help you understand that many people who have a lot of stored toxins in their systems will experience unpleasant symptoms as the toxins are displaced by iodine. Liver Cleansing (especially with herbs), fasting, colon cleansing and parasite cleansing will also produce cleansing crises and die off symptoms as they begin to clean the body of long accumulated toxins.