Swollen lymph nodes in the neck are most often caused by common infections, particularly viral upper respiratory infections and strep throat. Your neck contains dozens of lymph nodes organized in groups that filter fluid from your face, scalp, mouth, throat, and ears. When those areas encounter an infection or other threat, the nearby nodes ramp up immune activity and swell. In most cases, the swelling resolves on its own within two to three weeks.
Why Lymph Nodes Swell
Lymph nodes are small, bean-shaped structures that act as checkpoints for your immune system. Fluid from nearby tissues drains through them, and inside each node, immune cells scan for bacteria, viruses, or other foreign material. When they detect a threat, the node recruits more immune cells, and new blood and lymphatic vessels rapidly form within it. This flood of cellular activity is what makes the node physically larger and sometimes tender to the touch.
The swelling essentially means the node is doing its job. Once the threat is cleared, the node gradually returns to its normal size. Nodes smaller than about 1 centimeter across (roughly the width of a pencil eraser) are generally considered normal. Above that size, and especially above 1.5 to 2 centimeters, further evaluation may be warranted depending on how the node feels and how long it’s been there.
Viral Infections: The Most Common Cause
The common cold, flu, and other upper respiratory viruses are responsible for the majority of swollen neck nodes. These infections typically cause swelling on both sides of the neck at once, because the virus affects the entire throat and nasal area rather than one localized spot. The nodes are usually soft, mildly tender, and movable under the skin. This type of swelling tends to resolve within 7 to 10 days as the infection clears.
Infectious mononucleosis, caused by the Epstein-Barr virus, is another well-known trigger. Mono tends to produce more prominent, longer-lasting swelling that can take several weeks to fully resolve. It often comes with extreme fatigue, sore throat, and fever.
Bacterial Infections
Strep throat and staph skin infections are the bacterial causes doctors see most frequently. Unlike viral infections, bacterial infections often cause swelling on just one side of the neck. Staph and strep bacteria account for 40% to 80% of cases of acute one-sided neck node swelling. The affected node is typically painful, warm, and may be visibly red if the infection is severe enough to form an abscess beneath the skin.
Dental infections, ear infections, and skin wounds on the face or scalp can also trigger swelling in specific node groups. The location of the swelling often points to the source: nodes under the chin drain the lower lip and front of the tongue, nodes along the jawline drain the cheeks and floor of the mouth, and nodes along the side of the neck drain the throat, ear canal, and larynx.
Cat-scratch disease, caused by bacteria transmitted through a cat scratch or bite, is a common cause of neck swelling that lingers for weeks to months rather than days. Tuberculosis and other mycobacterial infections can also cause persistent, slowly enlarging nodes.
Autoimmune and Inflammatory Conditions
Several autoimmune diseases can trigger neck node swelling that isn’t related to infection. Lupus, rheumatoid arthritis, and Still’s disease all cause the immune system to stay in a heightened state, which keeps lymph nodes chronically active. The swelling in these cases tends to be generalized, affecting nodes in the neck and elsewhere in the body.
Sarcoidosis, a condition where clusters of inflammatory cells form in various organs, is another recognized cause. Less common conditions like Castleman disease, Kawasaki disease, and Kikuchi-Fujimoto disease can also present with prominent neck swelling, sometimes as an early or primary symptom.
Cancer-Related Swelling
Cancer is a less common but important cause of swollen neck nodes. It falls into two categories: lymphoma (cancer that starts in the lymph nodes themselves) and metastatic cancer (cancer that has spread to the nodes from somewhere else).
Hodgkin lymphoma typically starts in one group of neck nodes and spreads in an orderly pattern to neighboring groups. Non-Hodgkin lymphoma more often causes widespread swelling across multiple areas. Lymphoma nodes tend to feel rubbery or firm, are painless, and move freely under the skin, at least early on. Systemic symptoms like unexplained fevers, drenching night sweats, significant weight loss, and persistent itching (collectively called “B symptoms”) often accompany lymphoma and are a major reason to seek evaluation.
Metastatic deposits from cancers of the head, neck, or thyroid can also enlarge neck nodes. These nodes tend to feel hard, are fixed in place rather than movable, and are painless. Enlarged nodes just above the collarbone carry the highest suspicion for malignancy and always warrant investigation.
How the Nodes Feel Matters
The physical characteristics of a swollen node provide real diagnostic information. Soft, tender, movable nodes almost always point to infection. Rubbery, painless, mobile nodes are more characteristic of lymphoma. Hard, fixed, painless nodes suggest metastatic cancer or, less commonly, a granulomatous infection like tuberculosis. These are guidelines, not absolutes, but they are one of the first things a clinician assesses during an exam.
How Long Swelling Typically Lasts
Swelling that resolves within two to three weeks is classified as acute and is almost always caused by a straightforward infection. Swelling lasting two to six weeks is considered subacute and may point to cat-scratch disease, a mycobacterial infection, or a resolving viral illness like mono. Swelling persisting beyond six weeks is chronic and needs further investigation regardless of how the node feels.
It’s worth knowing that nodes don’t always shrink back to their original size. After a significant infection, a node may remain slightly enlarged but stable for months. This is different from a node that is actively growing.
Warning Signs That Need Evaluation
Most swollen neck nodes are harmless and self-limiting. But certain features raise concern and should prompt a visit to your doctor sooner rather than later:
- Size over 2 centimeters that persists beyond six weeks
- Firm, fixed, or matted nodes (nodes that feel stuck together or to surrounding tissue)
- Supraclavicular location (just above the collarbone)
- Systemic symptoms like unexplained fevers, night sweats, unintentional weight loss, or persistent fatigue
- No improvement after antibiotics when a bacterial infection was suspected
- Pallor or unusual bruising, which could suggest a blood-related disorder
For low-risk swelling, no testing is typically needed. If the picture is less clear, blood work and an ultrasound are common first steps. When malignancy is a real concern, a biopsy of the node provides a definitive answer.