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. Treatment may include an antibiotic (if bacterial), warm compresses, increasing fluid intake and good oral hygiene. Most salivary gland infections go away on their own or are cured with treatment. Complications are not common.

Sialadenitis is most commonly due to bacterial infections caused by Staphylococcus aureus. Other bacteria which can cause the infections include include streptococci, coliforms, and various anaerobic bacteria. Although less common than bacteria, several viruses have also been implicated in sialadenitis. These include the mumps virus, HIV, coxsackievirus, parainfluenza types I and II, influenza A, and herpes.

Signs and symptoms of sialadenitis may include fever, chills, and unilateral pain and swelling in the affected area. The affected gland may be firm and tender, with redness of the overlying skin. Pus may drain through the gland into the mouth.

In addition, since sialadenitis usually occurs after decreased flow of saliva (hyposecretion), patients are usually advised to drink plenty of fluids and eat or drink things that trigger saliva flow (such as lemon juice or hard candy). Warm compresses, and gland massage may also be helpful if the flow is obstructed in some way. Good oral hygiene are also important. Occasionally an abscess may form which needs to be drained especially if it proves resistant to antibiotics (or antiviral medication)

In rare cases of chronic or relapsing sialadenitis, surgery may be needed to remove part or all of the gland. This is more common when there is an underlying condition which is causing the hyposecretion.

In chronic or relapsing sialadenitis, the prognosis depends on the underlying cause of the infection.