Swollen lymph nodes in the neck are almost always a sign that your immune system is fighting something, most commonly a viral upper respiratory infection like a cold or the flu. Your neck contains dozens of lymph nodes organized in chains that filter fluid draining from your mouth, throat, sinuses, ears, and scalp. When any of those areas encounter an infection, the nearby nodes ramp up immune cell production and swell. In most cases, the swelling resolves on its own within two to three weeks.
What Happens Inside a Swollen Lymph Node
Lymph nodes are small, bean-shaped structures packed with immune cells. They act as filters and staging areas. Fluid from nearby tissues flows through them, and specialized immune cells inside scan that fluid for anything dangerous. Macrophages lining the interior of the node have been described as “cellular flypaper” because of how effectively they grab bacteria, viruses, and debris from the lymphatic fluid.
When a threat is detected, things move fast. Within 30 minutes of an infection in nearby tissue, large numbers of neutrophils (a type of white blood cell) flood into the node through blood vessels and begin swarming to contain the invader. Natural killer cells that normally reside in the node shift their behavior, migrating toward the threat and ramping up their activity. Meanwhile, the node begins producing more lymphocytes, the immune cells responsible for building a targeted response to the specific pathogen. All of this cellular activity, the influx of immune cells, increased blood flow, and fluid accumulation, is what makes the node physically swell and sometimes become tender to the touch.
The Most Common Causes
The single most frequent reason for swollen neck nodes is a viral upper respiratory infection. A cold, the flu, or a sinus infection will commonly cause nodes on both sides of the neck to enlarge. Strep throat is the most common bacterial cause, and it tends to produce swelling under the jaw and along the upper part of the neck. These infections are usually self-limited, meaning the swelling goes down as the infection clears.
Mononucleosis, caused by the Epstein-Barr virus, is a well-known cause of prolonged neck node swelling that can last weeks or even months. Cytomegalovirus, a related virus, can produce a similar pattern. Both tend to cause swelling on both sides of the neck rather than just one.
Dental problems are an underappreciated cause. A tooth abscess or gum infection drains into the submandibular nodes, the ones just below your jawline. If you have a swollen node under your jaw and you’ve also been having tooth pain or sensitivity, the two are likely connected. Ear infections, tonsillitis, and skin infections on the scalp or face can also trigger swelling in the nearest chain of nodes.
Which Nodes Swell Tells You Where the Problem Is
Your neck has several distinct groups of lymph nodes, and each group drains a specific area. This is why the location of your swollen node can hint at the underlying cause.
- Under the chin: Drains the floor of the mouth, the front of the tongue, and the lower lip. Swelling here often points to a dental or mouth issue.
- Under the jaw (submandibular): Drains the oral cavity and is commonly involved in tooth infections and sore throats.
- Along the side of the neck (upper and middle jugular): Drains the throat, tonsils, nasal passages, and voice box. These are the nodes most often swollen during colds, strep, and mono.
- Behind the ear or at the back of the neck (posterior): Drains the scalp and back of the throat. Scalp infections or rubella can cause swelling here.
- Just above the collarbone (supraclavicular): This location is more concerning. These nodes drain deeper structures, and swelling here is more strongly associated with serious conditions.
How to Tell Reactive Swelling From Something More Serious
Most swollen lymph nodes are “reactive,” meaning they’re simply reacting to a nearby infection and will return to normal size once the infection resolves. Reactive nodes are typically tender, soft, and movable under the skin. You can push them around a little with your fingers. They often appear on both sides of the neck at once.
Clinically, a neck lymph node is considered enlarged when it exceeds about 8 to 9 millimeters in its shortest diameter, roughly the width of a pencil eraser. Many people can feel nodes that are technically within normal size, especially if they’re thin or have long necks, so feeling a small lump doesn’t automatically mean something is wrong.
Certain characteristics raise the level of concern. A node that is painless, very hard or firm, feels irregular or lumpy, or doesn’t move when you push on it has a higher chance of being something other than a simple infection. Nodes that feel matted together, as if clumped into a mass rather than individual round bumps, also warrant closer attention. And swelling that appears just above the collarbone is taken more seriously regardless of how the node feels.
Red Flags Worth Knowing
A swollen node accompanied by certain systemic symptoms needs prompt evaluation. These include unexplained weight loss of more than 10% of your body weight, drenching night sweats (not just feeling warm at night, but soaking through your clothes or sheets), and persistent fevers without an obvious infection. These are sometimes called “B symptoms” and can be associated with lymphoma.
Other risk factors that increase the likelihood of a more serious cause: being over 40, swelling that persists beyond four to six weeks without shrinking, swelling in multiple regions of the body at once (not just the neck but also the armpits or groin), and nodes that haven’t returned to their baseline size after eight to twelve weeks. None of these factors on their own mean cancer, but the more that overlap, the more important it becomes to get checked.
Autoimmune and Other Non-Infectious Causes
Infections aren’t the only trigger. Some autoimmune conditions cause the immune system to produce excessive numbers of lymphocytes, leading to persistent node enlargement. In autoimmune lymphoproliferative syndrome, for example, swollen nodes in the neck, armpits, and groin are often the most visible symptom, and the swelling can last for months or years. Lupus and sarcoidosis can also produce chronic lymph node enlargement, usually alongside other symptoms like joint pain, skin changes, or fatigue.
Certain medications can cause generalized lymph node swelling as a side effect, and some sexually transmitted infections can trigger neck node enlargement if they involve the throat.
What to Expect if You Get It Checked
If your swelling is new and you have an obvious cold or sore throat, most clinicians will simply monitor it. The standard approach is to watch for two to four weeks to see if the node shrinks as the infection resolves.
If the swelling persists or has concerning features, the next step is usually an ultrasound. This painless imaging test lets a clinician measure the node precisely, check its internal structure, and look for features like abnormal blood flow patterns or the loss of the normal fatty center that healthy nodes have. Blood work may be ordered to check for mono, signs of infection, or other conditions.
If imaging and blood work don’t provide a clear answer and the node remains enlarged beyond eight to twelve weeks, a biopsy may be recommended. This involves removing part or all of the node to examine the cells under a microscope. It’s the most definitive way to rule out lymphoma or metastatic cancer.
For the vast majority of people who find a swollen node in their neck, the cause turns out to be a routine infection that resolves without any treatment beyond rest and time. The nodes themselves may take a few weeks to fully shrink back down even after you feel better, which is normal.