Sialadenitis is an infection of the salivary glands. It is usually caused by a virus or bacteria. The parotid (in front of the ear) and submandibular (under the chin) glands are most commonly affected. Sialadenitis may be associated with pain, tenderness, redness, and gradual, localized swelling of the affected area. Sialadenitis most commonly affects the elderly and chronically ill especially those with dry mouth or who are dehydrated, but can also affected people of any age including newborn babies. Diagnosis is usually made by clinical exam but a CT scan, MRI scan or ultrasound may be done if the doctor suspects an abscess or to look for stones.