I have completed a little more research on this post. Much of what I have dug up so far deals with Iodine detox reactions being the result of mineral deficiencies. If this is indeed the case, it could mean that the allergic reaction may also be due to mineral deficiencies of one or more minerals.
Much of the reading stating this also agrees that no one is "allergic" to Iodine as it is an essential element for many functions.
Do a search for Iodine allergy and mineral deficiencies... or deficiency.
I believe most allergies to be a result of one mineral or elemental deficiency/imbalance, or another. The rest of the allergies a result of generational adaptation that could be moved back to center gradually over time, if one knew exactly what to do and what needs were to be met; perhaps within a generation's lifetime.