Just a thought: have you ever taken fluoride based antidepressants like prozac or fluoride based Antibiotics like cipro? The zapping you've described are listed side effects of these meds. If you've taken such fluoride based meds in the past, it is possible that Iodine is chelating the fluoride. Uniquity (Natural Healing) helps folks who have been on anti-depressants in the past and in the process of healing, and detoxing some of the side effects of those drugs appear even though it may have been years since the person had taken them.
It could also be mercury being stirred up. Do you have Amalgam fillings?