Blockage: Blockage of the main parotid duct, or one of its branches, is often a primary cause of acute parotitis, with further inflammation secondary to bacterial superinfection. The blockage may be from a salivary stone, a mucous plug, or, more rarely, by a tumor, usually benign. Salivary stones, also called salivary calculi, are mainly made of calcium, but do not indicate any kind of calcium disorder. Stones may be diagnosed via X-ray (with a success rate of about 80%) or a computed tomography (CT) scan. Stones may be removed by manipulation in the doctor's office, or, in the worst cases, by surgery. Lithotripsy, also known as "shock wave" treatment, is best known for its use breaking up kidney stones. Lithotripsy can now be used on salivary stones as well. Ultrasound waves break up the stones, and the fragments flush out of the salivary duct.
Sjögren's syndrome: Chronic inflammation of the salivary glands may also be an autoimmune disease known as Sjögren's syndrome. The cause is unknown. The syndrome is often characterized by excessive dryness in the eyes, mouth, nose, vagina, and skin.
Other diseases: Swelling without pain and without infection also constitutes a form of parotitis, which may be acute or chronic. Diabetes, alcoholism, and bulimia may cause enlarged parotid glands, usually without pain. A small percentage of people with AIDS may experience parotitis.