A cleft in the middle of the tongue may be caused by congenital factors, poor oral hygiene and median rhomboid tongue infection. 1. Congenital factors: Congenital factors are generally a kind of chromosomal dominant genetic disease, which leads to the phenomenon of a cleft in the middle of the tongue. 2. Poor oral hygiene: when the patient does not pay attention to oral hygiene, it is easy for bacteria to invade and repeatedly stimulate the tongue, which will lead to the symptom of a cleft in the middle of the tongue. 3. Lingual inflammation: Lingual inflammation may be caused by Candida infection or endocrine disorders, and the patient will have the symptom of a fissure in the middle of the tongue, and some of the patients will also have the symptom of swelling and numbness at the fissure. When the patient has a crack in the middle of the tongue, it is necessary to go to the hospital in time to find out the cause of the disease and then carry out targeted treatment.