i have a white tounge for years , i believe its a combo factors that cause it. lots carbs, lots toxin,and a fungus.
so finaly, i do wash it with HP 3% super market brand, you`ll see what kind a foam on the toungue after you use HP as mouth wash., some times i mix it with water as 50\50, it works too, for a 50\50 i use full mug .