The main causes of crooked mouth are peripheral facial paralysis and central facial paralysis. When a crooked mouth occurs, it is important to seek medical treatment in time to avoid aggravating the condition due to delayed treatment. 1. Peripheral facial paralysis: Facial neuritis can cause peripheral facial paralysis. The onset of the disease is relatively acute, with symptoms such as paralysis of the affected side of the face, showing teeth, and crooked mouth. The disease usually reaches its most severe stage within 48 hours of onset. 2. Central facial paralysis: It is mainly related to cerebrovascular diseases. When people suffer from cerebral hemorrhage, cerebral infarction, tumor and other diseases, the intracranial nerves will be compressed, and there will be symptoms such as crooked mouth, dizziness, headache, slurred speech, and numbness and weakness of the affected side of the limbs. Crooked mouth may also be caused by other reasons, and should seek medical treatment in time.