Systematic Procedure of Tongue Diagnosis

The patient’s face is turned to the light and the tongue is examined in a flat, stretched out position, not, however, to the extent that its natural color changes (Fig. 17). It is best to examine the tongue by daylight. If, under certain conditions, the examination has to be done by artificial light, the wrong results may be obtained. If the tongue has to be examined initially by artificial light, it is advisable to examine it again later on by daylight. It is important to distinguish between the true color of the tongue and a discoloration caused by certain foods, medication, or mechanical influences. Milk, for instance, leaves a white coating on the surface of the tongue, coffee a brown surface. Bilberries (blueberries) and beet tinge the tongue bluish-red, whereas colored sweets make the tongue look green, yellow, or blue. Chocolate leaves a brown smear; toothpaste can leave a white layer, etc. The coating on the tongue can also be changed by brushing it with a toothbrush or after eating certain kinds of food. Food can be responsible for rubbing off a thick coating and thus make the coating look thinner or even normal. Hot, pungent, and spicy food can change the color of the tongue, leaving it either bright red or dark purple. For these reasons, the physician should never examine the tongue immediately after the patient has eaten, drunk, or brushed his or her teeth and tongue.