Dry mouth, or xerostomia, occurs when there is not enough saliva (or "spit") to lubricate the tongue, gums, and inside of the cheeks. Saliva is critical for chewing, swallowing, digestion ...

Products containing thymol, menthol, witch hazel, peroxides and eucalyptus can also cause a yellow coating on the tongue, if the mouth is especially dry. Dehydration can lead to a yellow tongue ...