Hi Doc, My tongue has turned dark reddish on the side walls. I am getting the similar pain like the pain during mouth ulcers. When i googled on it few websites mentioned it as vitamin deficiency and some say its a kawasaki disease. Please let me know if it is a normal deficiency or a serious condition to bother. Recently during a total body scan i got to know my thyroid levels are higher i. e 7 (ideally should be below 4) and i am following the diet and medicines since a month. So is the tongue issue one of the after effects of thyoid?