What Is a Lymph Node and Why Does It Swell?

Most people notice swollen lymph nodes at some point—usually in the neck, under the jaw, armpits, or groin. These small, bean-shaped glands are part of your immune system, and swelling is often a sign that your body is fighting something off.

What Do Lymph Nodes Do?

Lymph nodes filter lymphatic fluid, trapping viruses, bacteria, and abnormal cells. When the immune system is activated, lymph nodes fill with extra white blood cells and become enlarged.

Common Causes of Swollen Lymph Nodes

Infections:The most frequent cause. Viral infections (like colds or mononucleosis) and bacterial infections (such as strep throat or skin infections) can make nodes swell.

Immune reactions:Conditions like lupus or rheumatoid arthritis may lead to persistent swelling.

Skin conditions:Rashes, acne, or scalp infections can cause nearby lymph nodes to enlarge.

Dental or throat problems:Tooth infections, tonsillitis, and sinus infections often cause swollen neck nodes.

Cancer:Far less common. Cancers such as lymphoma or leukemia, and cancers that spread to lymph nodes, can cause painless, firm swelling.

What Swollen Nodes Feel Like

Swollen lymph nodes can feel:

• Tender

• Soft or rubbery

• Mobile (able to move under the skin)

Nodes associated with more serious causes tend to be:

• Firm or hard

• Fixed in place

• Persistently enlarged for weeks to months

• Accompanied by symptoms such as fevers, night sweats, or weight loss

When to Seek Medical Care

See a clinician if:

• Swelling lasts longer than 3–4 weeks

• Nodes are hard, fixed, or painless

• You have fever, night sweats, or unexplained weight loss

• The swelling is getting worse instead of improving

Most swollen lymph nodes are harmless and resolve as the underlying issue improves.