A dog’s tongue has many functions, including dissipating heat, distinguishing tastes and odors, grooming hair, sterilizing, etc. The color of the tongue can also be used to determine whether the dog is sick. If the dog's tongue is white, it may be caused by insufficient blood and malnutrition; if it is yellow, it may be chronic hepatitis; if it is bluish-purple, it may be cardiopulmonary disease; if it is red, it may be a thermal infection disease.