Swollen neck glands are almost always a sign that your immune system is responding to something, most commonly an everyday infection like a cold or sore throat. The lumps you feel are lymph nodes, small bean-shaped filters packed with immune cells that trap and fight germs draining from your head, mouth, ears, and throat. When they ramp up to fight an infection, they can swell from their normal size (under 1 cm) to noticeably tender bumps along your jaw, behind your ears, or down the sides of your neck.
Why Lymph Nodes Swell
Lymph nodes are scattered throughout your body, but the ones in the neck sit along the drainage routes for your sinuses, throat, teeth, scalp, and ears. When an infection or other threat enters nearby tissue, immune cells inside the node begin multiplying rapidly. The structural cells that form the node itself also grow and switch on large numbers of genes to support this immune response. Blood flow to the node increases, fluid accumulates, and the node physically expands. That’s the tender lump you feel under the skin.
Research from the University of Melbourne found something interesting about this process: once the infection clears, the structural cells return to their normal gene activity, but the node stays slightly larger than it was before. It essentially retains a memory of the infection, allowing it to respond faster and more effectively if the same threat returns. This means a lymph node you felt during a bad cold may remain faintly palpable for weeks afterward, even though you’ve fully recovered.
Viral Infections: The Most Common Cause
A viral upper respiratory infection is the single most common reason for swollen neck glands, especially in children. The common cold, flu, and other respiratory viruses cause temporary, bilateral swelling (both sides of the neck) that usually resolves within one to two weeks as the infection clears.
Other viral causes include:
- Mononucleosis (Epstein-Barr virus), which often produces large, tender nodes along with extreme fatigue and sore throat, particularly in teenagers and young adults
- Cytomegalovirus (CMV), a related virus that can cause a mono-like illness
- Rubella, which characteristically swells nodes behind the ears and at the back of the neck
With viral infections, nodes are typically soft, movable, and tender to the touch. They usually shrink on their own once your body clears the virus.
Bacterial Infections
Bacterial infections tend to cause more localized, one-sided swelling and can make nodes significantly larger and more painful than viral causes. The most frequent bacterial triggers are Staphylococcus aureus and group A streptococcus (the bacteria behind strep throat). Dental infections and abscesses caused by anaerobic bacteria are another common culprit, often producing swollen glands under the jaw on the same side as the bad tooth.
Less common bacterial causes include cat scratch disease, caused by a bacterium transmitted through a cat’s scratch or bite, and tuberculosis, which can produce persistent, firm lymph node swelling in the neck that doesn’t respond to standard antibiotics.
Autoimmune and Inflammatory Conditions
Not all swollen neck glands point to infection. Several autoimmune conditions can trigger lymph node enlargement because they keep the immune system in a state of chronic activation. Rheumatoid arthritis, lupus, and Still’s disease (a form of inflammatory arthritis) all list swollen lymph nodes among their symptoms, typically affecting nodes in the neck and other areas simultaneously.
Sarcoidosis, a condition where clusters of inflammatory cells form in various organs, can also cause persistent neck node swelling. Kawasaki disease, which primarily affects young children, produces swollen cervical nodes along with fever, rash, and redness of the eyes and mouth.
Medications That Cause Swelling
Certain medications can trigger lymph node enlargement as a side effect. These include some blood pressure medications (like atenolol and captopril), seizure medications (like carbamazepine and phenytoin), certain antibiotics (including penicillin), and allopurinol, which is used for gout. If swollen glands appeared shortly after starting a new medication, that timing is worth mentioning to your doctor.
Cancer-Related Causes
Lymph node swelling from cancer is far less common than infectious causes, but it’s often what people worry about most. Lymphomas (cancers of the lymphatic system itself) can present as painless, firm, enlarged nodes. The classic “B symptoms” of Hodgkin lymphoma are unexplained fever, drenching night sweats, and weight loss exceeding 10% of your normal body weight. These symptoms appear in about 8% of early-stage cases but rise to 68% in advanced disease.
Nodes can also swell when cancer from a nearby structure spreads to them. The location of the swollen node can offer clues: nodes high along the side of the neck may receive drainage from cancers of the mouth, throat, or salivary glands; nodes lower in the neck are more associated with the thyroid, larynx, or esophagus. Swelling in the supraclavicular area, just above the collarbone, is considered more concerning and warrants prompt investigation.
Where the Swelling Is Matters
Your neck contains several distinct groups of lymph nodes, and the location of the swelling can help narrow down the cause. Nodes under the jaw (submandibular) commonly react to dental infections, mouth sores, or throat infections. Nodes behind the ear often swell with scalp infections or rubella. Nodes running along the side of the neck respond to a wide range of head and throat infections.
Supraclavicular nodes, the ones sitting just above the collarbone, deserve special attention. Swelling in this area is less likely to be from a simple infection and more often warrants further testing, as these nodes can receive drainage from the chest and abdomen in addition to the head and neck.
What “Normal” Swelling Looks Like
Most swollen neck glands from infection share a few features: they’re tender, soft or slightly rubbery, movable under the skin, and usually less than 2 cm across. They develop alongside other symptoms like a sore throat, runny nose, or fever, and they shrink over one to three weeks as the illness resolves.
Characteristics that raise more concern include nodes that are hard or fixed in place (not movable), painless enlargement that persists beyond three to four weeks, nodes larger than 1 cm that keep growing, or swelling accompanied by unexplained weight loss, persistent fevers, or night sweats. Clinical guidelines generally recommend that lymph nodes persisting beyond three to four weeks without a clear explanation should be evaluated further.
How Swollen Glands Are Evaluated
If your swollen glands don’t resolve on their own, the first step is usually a physical exam and a review of your symptoms, recent illnesses, medications, and any exposures (like a cat scratch or recent travel). Blood tests can check for signs of infection, inflammation, or blood cancers.
When imaging is needed, ultrasound is typically used first for children under 14, while CT scans are preferred for older teenagers and adults. On imaging, a round (spherical) node larger than 10 mm is more suspicious, while an oval-shaped node with a visible fatty center is more reassuring.
If the cause still isn’t clear, a biopsy may be recommended. This can range from a fine-needle aspiration, where a thin needle draws out a small sample of cells, to a core needle biopsy or full surgical removal of the node for examination. The largest, most accessible, and most suspicious-looking node is the one typically sampled.