The parotid glands are the largest of the three major salivary glands, situated on either side of the face, just in front of and below each ear. They produce serous saliva, a watery fluid rich in enzymes that is secreted into the mouth via Stensen’s duct to begin digestion and lubricate the oral cavity. Swelling of these glands indicates inflammation or an obstruction that prevents the normal flow of saliva. This enlargement can be a sudden, painful event or a gradual, long-term change.
Acute Infectious Causes
Infections represent a frequent cause of sudden parotid gland swelling, often presenting with pain and rapid onset. Viral infections are common culprits, with mumps being the most historically recognized cause, although its incidence has dropped significantly due to widespread vaccination. Mumps, caused by a paramyxovirus, typically results in painful swelling of one or both parotid glands, accompanied by general symptoms like fever and headache.
Other viruses, including influenza, parainfluenza, and coxsackievirus, can also trigger acute parotitis. The Epstein-Barr virus (EBV) or Human Immunodeficiency Virus (HIV) can cause parotid enlargement, often characterized by non-painful, chronic, or recurrent bilateral swelling due to the formation of lymphoepithelial cysts. Viral parotitis is a self-limiting condition that resolves within a week or two.
Bacterial infections cause acute suppurative parotitis, which is more severe and is commonly seen in older, dehydrated, or debilitated patients. This condition is usually unilateral and presents with painful swelling of the gland. The most common bacterial agent is Staphylococcus aureus, which ascends from the mouth due to reduced salivary flow. Bacterial parotitis often involves pus discharging from Stensen’s duct, accompanied by a high fever and general malaise.
Mechanical Blockages and Stones
Physical obstructions within the salivary duct system are a cause of parotid swelling related to meal times. Sialolithiasis, the formation of salivary stones, involves the crystallization of mineral deposits, primarily calcium phosphate, within the duct or the gland itself. While stones are more prevalent in the submandibular gland, they can form in the parotid gland’s duct, Stensen’s duct, leading to a blockage.
“Mealtime syndrome” is the primary symptom of a mechanical blockage. Eating triggers the gland to produce a large volume of saliva. When this saliva cannot pass the stone, the gland swells rapidly and painfully, causing an acute sensation of pressure near the ear or jaw. The swelling gradually subsides as the saliva is slowly reabsorbed or forces its way past the obstruction, only to recur at the next meal.
Chronic and Systemic Conditions
Swelling that is long-lasting, recurrent, or involves both glands suggests an underlying systemic disorder or a structural issue. Autoimmune conditions affect the parotid glands, with Sjögren’s Syndrome being the most prominent example. This condition is characterized by the immune system attacking the glands responsible for moisture production, resulting in chronic or recurrent bilateral parotid swelling alongside severe dry eyes and dry mouth.
Structural abnormalities, such as the development of masses and tumors, cause persistent swelling. Swelling caused by a tumor is typically firm to the touch, unilateral, and often painless in its early stages. This helps differentiate it from the tender, inflammatory swelling of an infection.
Sialadenosis describes a non-inflammatory enlargement of the parotid glands that is usually non-tender and bilateral. This condition is often linked to underlying metabolic or endocrine issues, such as poorly controlled diabetes, alcoholism, or malnutrition. Certain medications, including some psychotropic drugs and antihypertensives, can be associated with chronic, non-tender parotid swelling as a side effect.