Parotitis means inflammation of the parotid glands and one or both parotid glands can get inflamed. These are the largest salivary glands that are located in front of the ear one on each side.
Some common causes of inflammation include
Bacterial infection: Older people are at risk of bacterial infection as they are often on medications that cause dry mouth (xerostomia), or are dehydrated or weakened by chronic diseases. Reduced flow of saliva allows the bacteria to collect and grow in the duct that drains saliva from the parotid gland in the mouth. This can lead to infection in the gland.
Stone: Stone in the parotid glands can block the drainage of saliva and cause infection.
Mucus plugs: Mucus plug in the duct can block the drainage of saliva from the gland to the mouth and cause infection.
Other causes that can cause parotitis include sjögren's syndrome, viral infections, AIDS, and rarely a tumor. Certain diseases such as diabetes, alcoholism and bulimia can lead to enlargement of parotid glands, but these conditions usually do not cause pain or infection.