Lymph nodes are critical parts of the immune system, filtering foreign substances from the body, and storing white blood cells, called lymphocytes, that are ready to fight disease and infections.

You have hundreds of small bean-shaped lymph nodes throughout the body, including the:

  • neck
  • armpit
  • chest
  • abdomen
  • groin

Swollen lymph nodes, also known as lymphadenitis, in the armpit indicate that your body is responding to an infection, injury, or a disease, like cancer. It’s important to keep in mind that in most cases, a swollen lymph node in the armpit isn’t a sign of cancer.

It’s not a symptom to dismiss either, as it may be a sign of a condition that requires medical attention.

A lymph node in the armpit that’s only slightly enlarged may be difficult to see, but you may be able to feel it with your fingers. A serious infection or other condition may cause one or more nodes to swell enough that you can see a lump under your skin.

Keep in mind that the armpit contains many nodes, so swelling could occur in the front, center, or back of the armpit, as well as along part of the upper arm near the armpit.

In addition to being swollen, an affected lymph node may also be sore or tender to the touch.

To check for a swollen lymph node in the armpit, lift that arm slightly and gently place your fingers into that armpit. Press your fingers against the center of the armpit and then around the front and back of the armpit along the chest wall. Do the same on the other side.

Lymph nodes exist in pairs on each side of the body, and typically only one node in a pair will be swollen. By comparing both sides, it should be a little easier to tell if one is enlarged.

If lymph nodes are swollen in more than one part of the body, the condition is known as generalized lymphadenopathy, which suggests a systemic illness. Localized lymphadenopathy refers to swollen lymph node(s) in one location.

The location of swollen lymph nodes usually suggests the cause of the problem. A swollen lymph node in the neck, for example, is often a sign of an upper respiratory infection.

When lymph nodes in the armpit become swollen, your body may be fighting a viral infection, or any of several other conditions. Among the potential causes of a swollen lymph node in the armpit are:

Viral infection

Common viruses can trigger swelling in one or more lymph nodes in the armpit. They include the flu, common cold, and mononucleosis. More serious viral infections that may cause lymph node enlargement include herpes, rubella and HIV.

These viruses may also cause lymph nodes in the neck to become enlarged, too. In many cases, rest, fluids, and time are all that you can do while your immune system fights off the virus. For certain viral infections, like HIV, antiviral medications may be necessary.

Bacterial infection

Some common bacterial infections on the arm or surrounding chest wall, including staphylococcus and streptococcus, can lead to an enlarged lymph node in the armpit and elsewhere in the body. Antibiotics and rest are usually enough to overcome a bacterial infection.

Immune system disorder

Flare-ups of autoimmune disorders, like lupus and rheumatoid arthritis, can cause temporary enlargement of the lymph nodes in an armpit. Treatments vary, depending on the cause, but anti-inflammatory medications, pain relievers, and in serious cases, immunosuppressant drugs may be necessary.

Cancer

Certain types of cancer directly involve the lymphatic system. Lymphoma actually originates in the lymph glands. Leukemia, a cancer of the blood cells, can cause inflammation and swelling of the lymph nodes.

Cancers that form in other organs or tissue may spread to the lymphatic system. Breast cancer, for example, can cause swelling of the lymph nodes in the armpit.

An enlarged lymph node near a cancerous tumor is often suspected of also being cancerous. Cancer treatments vary, and may include chemotherapy, radiation therapy, surgery and other approaches.

Medications

In rare cases, certain medications can cause lymph nodes to swell. Among them are:

  • ACE inhibitors, beta blockers, and vasodilators to treat high blood pressure
  • anticonvulsant drugs, including phenytoin and primidone
  • anti-malarial drugs, including quinidine
  • uric acid reducers, like allopurinol

Switching medications or adjusting doses may be enough to reduce side effects, like lymph node enlargement.

As your body starts to successfully fight off the infection, the swelling in your lymph nodes should start to diminish.

With a typical bacterial infection, for example, a course of antibiotics should start to relieve lymph node swelling and other symptoms within a few days. A stubborn viral infection could take longer.

If your other symptoms are subsiding, but your lymph nodes remain swollen, tell a health professional. You may need additional treatment or a follow-up exam to see if there are other reasons your lymph nodes are still enlarged.

Because swollen lymph nodes are more often signs of an infection, rather than cancer, you may be inclined to dismiss swelling as a temporary symptom that’ll subside as you get over your infection. In many cases, that’s exactly what will happen.

If you’re unsure whether to seek a medical evaluation for swollen lymph nodes, consider these signs as reasons to see a medical professional:

  • One or more lymph nodes are swollen for no obvious reason.
  • The swelling has lasted or gotten worse over a period of 2 or more weeks.
  • The affected node feels hard and immovable when you press on it.
  • The swollen lymph nodes aren’t painful.
  • You have swollen lymph nodes in separate areas, like the armpit and groin.
  • You have other symptoms, like:
    • redness or fluid oozing around the node
    • fever
    • cough
    • night sweats
    • unexplained weight loss
    • pain elsewhere in your body

Most of the time, a swollen lymph node means your body’s immune system is doing its job in responding to an infection or other health problem. Of course that also means you’re dealing with an illness or injury that may require treatment.

If you’re battling a cold, for instance, and you notice slight swelling of a lymph node in your armpit, pay attention to it for a few days and see if the swelling goes down when you start feeling better.

But unexplained swelling or the presence of other serious symptoms should prompt a visit to a health professional for a more complete evaluation.