If we exclude that the tongue is black due to the consumption of dark food such as mulberry, the specific recovery time is related to the patient’s constitution, the cause of the disease, and the measures taken, so it needs to be analyzed on a case-by-case basis and cannot be generalized. A normal person has a thin white and moist tongue, while a person with a black tongue has a black tongue in the middle of the tongue. The black tongue moss may be caused by heat and fire. Patients with poor gastrointestinal function are prone to cold, and the tongue moss will become thick and greasy, white at first, then gradually turning yellow or black. Patients who often stay up late causing yin deficiency may also have a black tongue moss. Patients are advised to visit the internal medicine department of traditional Chinese medicine in a timely manner to have an interview with a professional doctor to determine the specific cause of the problem, and then to carry out appropriate conditioning or treatment, which can usually be recovered in about 10 days. In addition, patients with chronic diseases such as kidney disease may also experience black tongue when their condition worsens, and the recovery time for this condition varies somewhat individually and is usually not clear. Patients are advised to take part in sports to improve their immune system, have regular rest and rest, drink more water, and avoid spicy, stimulating and cold foods.