What causes swelling of the lymph nodes behind the ear?

Causes of postauricular lymphadenopathy are numerous. It may result from lymphadenitis or a pleomorphic adenoma of the parotid gland. Inflammatory conditions affecting the ear piercing site or auricle—such as otitis media, cochlear infection, or auricular infection—can also lead to lymph node enlargement. Oral ulcers or gingivitis may allow bacterial invasion of the lymph nodes, triggering an inflammatory response. Additionally, acute tonsillitis, acute pharyngitis, acute rhinitis, or acute sinusitis can cause postauricular lymphadenopathy.