Pain on one side of the face may be caused by the following reasons: first, it may be trigeminal neuralgia, trigeminal neuralgia is a kind of pain confined to the distribution area of the trigeminal nerve, and it is more common around the corner of the eye, the upper part of the cheeks and the lower jaw. The pain is short-lived, lasting only a few seconds or up to 2 minutes, with sudden onset and offset, and no pain in the intervals. The nature of the attack is pins and needles, electric shocks, burning, cutting or tearing, and can be triggered by movements such as washing the face, brushing the teeth, or eating. The patient’s face can have trigger points, such as the nose, corners of the mouth, cheeks or tongue, gently touching the area can trigger this pain. Secondly, it may be caused by the swelling of local lymph nodes, usually some upper respiratory tract infections, such as acute pharyngitis, acute tonsillitis caused by the enlargement of nearby lymph nodes and the appearance of pain on one side of the face, usually in the face of the lymph nodes can be felt to be enlarged, and there is pressure and pain of the symptoms of the local ultrasound basically can be diagnosed. Third, it may be caused by pulpitis, apical inflammation, inflammation or infection of the gums, usually accompanied by redness, swelling and toothache in the mouth on one side of the face.