The saliva inside the mouth is always coming out may be caused by glandular secretion, but also may be caused by facial nerve paralysis, mouth ulcers, and other causes such as caries. 1. Physiological factors: If the salivary glands and parotid glands in the mouth are secreting vigorously, but the amount of swallowing is small, so the organism will appear in the mouth always drooling performance. This is a normal physiological phenomenon, generally do not need treatment. 2. Facial nerve palsy: Facial nerve palsy may be caused by intracranial infection, trauma, cerebral infarction and other reasons. The patient will have salivation (drooling), slurred speech, crooked mouth and other manifestations, so the patient will have the symptom of drooling inside the mouth all the time. 3. Mouth ulcers: Mouth ulcers may be caused by heredity, decreased immunity, partiality, physical injury and so on. And mouth ulcers will stimulate the salivary glands, the patient will not only have the performance of saliva inside the mouth, but also have symptoms such as edema and burning sensation on the oral mucosa. 4. Other: patients with constant drooling inside the mouth may also be caries, gastroesophageal reflux, gingivitis and other causes. It is recommended that the symptoms of constant salivation inside the mouth need to consult a doctor in time, if it is caused by physiological factors, do not need to be treated. If it is caused by disease, you need to follow the doctor’s instructions for treatment.