There are many reasons for the blackness in the middle of the tongue, specifically the following reasons: 1. Some foods eaten in daily life, such as black sesame paste, sour plums, or when taking medication or iron supplements, may also cause blackness in the middle of the tongue; often staying up late, smoking too much, and keeping the mind in a highly stressful state for a long time can also cause blackness in the middle of the tongue, which is only temporary and need not be too worried. 2, The Chinese medicine believes that the middle of the tongue black may be gastrointestinal dysfunction, resulting in indigestion or hot pole fire, so it is recommended to develop good dietary rest habits and eat more fruit to supplement vitamins. 3, in daily clinical research shows that chronic diseases in the process of deterioration, will also appear in the middle of the tongue black phenomenon, such as uremia, sepsis, septic osteomyelitis, malignant tumors, etc., if this symptom appears, you need to seek medical attention for treatment in a timely manner.