Re: Iodine and dragging immune system
One thing that comes to mind is making sure you're getting vitamin A and D from food sources (and sunlight, in the case of D), not synthetic vitamins. Synthetic A and D cause problems and just aren't as helpful as those from food. You don't want to get those out of balance, like you don't want your copper/zinc ratio out of whack, or calcium/magnesium ratio.
The Weston A. Price Foundation (www.wapf.org) has articles with information explaining how to get vitamins A, D (and K, another fat-soluble one). Cod liver oil can be tricky because the usual deodorizing processing means they strip out the vitamins and add synthetic ones back in. I gave up on Carlson's for that reason and bought the expensive butter oil/cod liver oil/fish oil combination oil from Dr. Ron's. If you decide to go that route, the high-vitamin butter oil is so reduced from milk, I doubt you'd have problems if you have milk allergies normally. Some people who find themselves lactose intolerant can eat butter, and if not butter, then ghee, which has all those milk solids removed.
Other nutrients that work synergistically with vitamin D are calcium, magnesium, and boron.
Getting good fats (low polynunsaturates, high saturates, in the form of lard, tallow, butter, coconut oil) has helped me tremendously. That includes my immune system. I'm not out of the woods yet.