Hi Dear, Welcome to HCM. Understanding your concern. As per your query you have symptoms of yellow tongue which is mainly because of underlying medical condition such as celiac and thyroid along with smoking tobacco. Celiac and tobacco are autoimmune diseases which lower down body immunity and along with that smoking acts as additive effect and leads to poor immunity and body becomes susceptible to fungal/ yeast infections which leads to thrush and yellow coating on tongue. I would suggest you to maintain proper oral hygiene by brushing and flossing twice daily. Use anti fungal mouth wash such as Nystatin suspensions. Drink water in plenty to re hydrate body and replenish fluids. Use tongue scrapper to remove debris from tongue and coatings on tongue. Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry Maheshwari