Adrian - There is one way to check... stop the iodine for several weeks and see if your tongue normalizes.
When I began taking iodine, I noticed an uncomfortable, metallic taste and my nose ran continually. I stopped and the symptoms went away, confirming it was the iodine. Since I wanted to add iodine and since I felt the symptoms were part of a detoxing effect, I persisted with very slowly ramping up doses ... the metallic taste has gone but the nose still runs. The iodine experts say it's either a detox reaction or... a sensitivity to iodine. Since I've had the desired results of diminishing the size of thyroid nodules, I'm going to continue to use the iodine and tough-out the side effects.
If you stop the iodine and the numbness persists, then I'd start looking into a vitamin B deficiency. Tongue issues are among the first signs. We all need a substantial, complete B complex to ensure methylation, especially if we eat Paleo and eliminate grains. If you have a high stress load, all the more reason to take a substantial B Complex.
Be well, Jackie
