The area around the ear, often described as “behind the ear,” contains several structures that can become enlarged. When swelling occurs in this location, the most prominent structure involved is frequently the parotid gland. This gland is the largest of the major salivary glands, and its location near the ear canal and jawbone makes it a common source of noticeable swelling.
The Primary Structure: The Parotid Gland
The parotid gland is an irregularly shaped mass situated on the side of the face, primarily positioned just in front of and slightly below the ear canal. It extends backward to the mastoid process and covers a portion of the jawbone (mandibular ramus) and the masseter muscle. Although much of the gland is anterior to the ear, its lower pole projects into the area commonly perceived as “behind” the ear. The facial nerve runs directly through the gland, dividing it into a deep lobe and a superficial lobe.
Function of the Parotid Gland
The sole purpose of this structure is the production and secretion of saliva into the mouth. The parotid gland produces serous saliva, which is thin and watery. This saliva is rich in the enzyme amylase, which begins the chemical process of starch digestion. The fluid travels through Stensen’s duct, which crosses the cheek muscle and opens into the mouth near the upper second molar. Saliva production is stimulated by eating, but the gland contributes a small amount of saliva continuously.
Distinguishing the Parotid from Lymph Nodes
The region near the ear also houses a group of much smaller, bean-shaped structures known as lymph nodes. These nodes, specifically the pre-auricular and post-auricular groups, are part of the body’s immune system, not its digestive system. While the parotid gland is a large, fixed organ, lymph nodes are small, numerous, and often feel more mobile when enlarged. The lymph nodes function as filtration centers, trapping harmful substances like bacteria and viruses from the lymphatic fluid draining the scalp, face, and ear. Lymph nodes are even found embedded within the parotid gland itself, which can complicate the identification of swelling in this area.
Why These Glands Might Swell
Swelling in this region can be due to problems with either the parotid gland (parotitis) or the lymph nodes (lymphadenopathy).
Parotid Gland Swelling (Parotitis)
The most recognized cause of acute parotitis is a viral infection, specifically the mumps virus, which often causes painful, bilateral enlargement. Bacterial infections, frequently caused by Staphylococcus aureus or Streptococcus species, can also lead to parotitis, especially when saliva flow is reduced. Another common issue is the formation of salivary stones (sialolithiasis), which block the parotid duct. This blockage causes saliva to back up, resulting in painful swelling that often worsens during eating.
Lymph Node Swelling (Lymphadenopathy)
Lymphadenopathy is typically a direct response to a localized infection or inflammation. The post-auricular lymph nodes swell when filtering pathogens from the areas they drain, such as the ear canal, scalp, or skin behind the ear. Common causes include ear infections, scalp conditions like ringworm, or a scratch that causes cat scratch disease. Any persistent or unusually painful swelling in the area should be evaluated by a healthcare professional.