Children often unconsciously open their mouths may be caused by chronic rhinitis, oral ulcers and tic disorders. 1. Chronic rhinitis: As the child’s immune system is low, resulting in inflammation and infection of chronic rhinitis, symptoms such as nasal congestion and obstructed gasping for air may occur, and the child will relieve the symptoms by unconsciously opening his/her mouth. 2. Mouth ulcers: If the child suffers from mouth ulcers, or causes pain in the mouth as well as the symptom of drooling, the child will often open his mouth unconsciously at this time. 3. Tourette’s syndrome: If a child suffers from Tourette’s syndrome, it can also cause involuntary opening of the mouth, crooked mouth, and even blinking of the eyes. When a child frequently opens his or her mouth unconsciously and is accompanied by physical discomfort, it is recommended that he or she go to the pediatrician of the hospital in a timely manner for examination and treatment according to the cause of the disease.