Blue in the tongue may be physiological factors, but also may be the manifestation of certain diseases, such as local injury, hemangioma, etc., should be timely consultation to identify the cause of the disease. 1. Physiological factors: (1) thin mucosal tissue: some people due to thin mucosal tissue, and blood vessels more dense, rich, blood vessels through the thin mucosa, will be manifested in the tongue in the blue, mostly seen in the back of the tongue. This is a normal physiological phenomenon, no need to deal with, close observation can be. (2) Dietary factors: when eating food containing blue or green pigment, after chewing, the tongue may be stained with cyanosis. 2. Pathological factors: (1) Local injury: such as tooth bite, external physical and chemical stimulation, such as scalding, leading to corresponding stimulation of the blood vessels on the tongue, and the internal rupture of the capillaries, which is manifested as cyanosis. (2) Hemangioma: hemangioma is a tumor disease of endothelial cells of blood vessels, hemangioma, if it grows on the tongue, can lead to local skin congestion plaques, the deeper part of the location can appear bluish and bulging, and some patients may have pain. If the symptoms of greening in the tongue appear, it is recommended to consult a doctor in time and give targeted treatment after the doctor clarifies the cause of the disease.