Pain under the ear may be caused by mumps, a viral infection that occurs when the body’s resistance or immune system decreases. The parotid gland is swollen and painful, and the pain on the affected side is very pronounced when eating, i.e., when chewing food. Anti-viral treatment is needed, such as oral oseltamivir or intravenous ribavirin, which usually takes about a week to treat. It may also be caused by inflammation of the lymph nodes, which is a bacterial infection, commonly caused by Staphylococcus aureus or Streptococcus hemolyticus, resulting in redness, swelling and pain in the lower left lymph node of the patient. Oral antibiotics are needed for treatment, such as cefixime and levofloxacin, which are also usually needed to fight the infection for about a week.