Oral ulcers, commonly known as “mouth sores”, are superficial ulcers on the oral mucosa, which can range from the size of a grain of rice to a soybean, round or ovoid, with a concave ulcer surface and congestion around it, and can occur in any part of the oral mucosa, with the lips, tongue, cheeks or gums being the most common. When the mouth ulcer under the tongue, can be triggered by irritating food pain, common causes such as trauma factors, nutritional deficiency, mental factors, radiotherapy and chemotherapy, mouth ulcer recurrence, digestive disorders, other, etc. 1, trauma factors: refers to the oral mucosa local stimulation by external forces, such as accidentally biting their tongue when talking, or hard food scratching the oral mucosa, can form a tongue ulcer; 2, nutritional deficiency : Consider that the body lacks vitamins, followed by folic acid, iron, zinc and other trace elements, resulting in a decrease in the body’s immunity, which in turn increases the probability of oral ulcers; 3, mental factors: excessive emotional fluctuations, nervousness, fear and other psychological factors and irregular work and rest, etc., can lead to the appearance of sublingual ulcers; 4, radiotherapy and chemotherapy: long-term radiotherapy can cause a significant reduction in the number of white blood cells in the body, which in turn damages the normal oral mucosal cells, resulting in immune deficiency and causing sublingual ulcers; 5.Recurrence of oral ulcers: it can occur in the abdomen of tongue, sublingual area, etc., which can generally heal by itself in 1-2 weeks; 6.Digestive disorders: such as gastric ulcers, duodenal ulcers, etc., which can cause disease through immune system and trigger sublingual ulcers; 7.Other: if there are untreated sublingual ulcers or unexplained bleeding, it can be considered as signs of tongue cancer and needs promptly go to hospital for examination and early treatment. In addition, endocrine disorders caused by the increase of progesterone level and the decrease of estrogen level in the body before the arrival of menstruation in women can easily lead to the occurrence of mouth ulcers.