The parotid glands, the largest salivary glands, are located in front of and below each ear. They produce much of the saliva, which aids digestion, lubricates the mouth, and reduces harmful bacteria. Swelling in this area, called parotitis, signals an underlying issue. This swelling can stem from various factors, from infections to systemic diseases, making understanding its causes important for proper evaluation.
Infectious Causes
Viral infections frequently cause parotid gland swelling. Mumps, caused by the mumps virus (MuV), is a well-known example, often presenting with fever, headache, muscle aches, and fatigue before painful swelling of one or both parotid glands. Other viruses, including influenza, parainfluenza, Epstein-Barr, HIV, and COVID-19, can also lead to parotid enlargement.
Bacterial infections, or sialadenitis, also contribute to parotid swelling. This often occurs when saliva flow is reduced, such as from dehydration, poor oral hygiene, or a duct blockage. Common bacteria like Staphylococcus aureus can then proliferate, causing infection. Symptoms typically include pain, redness, tenderness, and sometimes pus drainage from the salivary duct.
Obstructive and Structural Issues
Physical obstructions within the salivary ducts are a common cause of parotid gland swelling. Salivary stones, or sialolithiasis, form when calcium and other minerals crystallize within the ducts, impeding saliva flow. This blockage leads to swelling and pain, often intensifying during or after eating as the gland attempts to produce saliva against the obstruction.
Tumors, both benign and malignant, can cause parotid gland swelling. Benign tumors, like pleomorphic adenomas and Warthin’s tumors, are more common and typically present as a firm, often painless lump that grows slowly. Malignant tumors, though less frequent, might grow more rapidly, cause persistent pain, or lead to facial nerve issues like weakness or numbness. Any persistent or growing lump in the parotid area warrants medical evaluation.
Systemic and Autoimmune Conditions
Systemic conditions and autoimmune disorders can cause parotid gland swelling. Sjögren’s syndrome is a prominent autoimmune disease where the immune system attacks moisture-producing glands, including salivary glands. This leads to chronic inflammation and enlargement of the parotid glands, often with dry mouth and dry eyes. Other autoimmune conditions, such as lupus or rheumatoid arthritis, can also involve the parotid glands.
Other systemic diseases, like sarcoidosis, can also cause parotid swelling. Sarcoidosis is an inflammatory disease characterized by granuloma formation in various organs, including the salivary glands. Parotid involvement in sarcoidosis can be painless and affect one or both glands. Conditions like diabetes can also contribute to recurrent parotid swelling, often by increasing infection susceptibility or affecting salivary gland function.
Medication-Related and Other Causes
Certain medications can induce parotid gland enlargement as a side effect. Drugs that reduce saliva production, such as some antihypertensives, antipsychotics (like clozapine), and anticholinergic agents, can predispose individuals to swelling. Reduced saliva flow can lead to inflammation or make glands more vulnerable to infection. Medication-induced swelling is often reversible once the offending drug is discontinued or adjusted.
Direct physical trauma to the parotid gland area can also result in temporary swelling. Rare inflammatory conditions can also affect the parotid glands, leading to enlargement. Any persistent or concerning parotid gland swelling should prompt consultation with a medical professional for proper diagnosis and management.