Swelling and pain below the root of the ear is mainly due to the following reasons: First, upper respiratory tract infection: acute upper respiratory tract viral infections can cause systemic reactive lymph node enlargement, the patient will appear behind the ear or jaw lymph node enlargement, redness, swelling and pain below the root of the ear, give blood tests or antiviral treatment, the symptom can be relieved. Second, acute parotitis: swelling and pain below the ear, but also to know whether the patient has a fever, whether there is a side of the face swelling, acute parotitis patients can also appear below the ear swelling and pain, at the same time there is facial swelling, the examination can be touched parotid gland enlargement. Third, other diseases that cause parotid enlargement, such as suppurative parotitis, parotid tumors and so on.