What Can Cause A Swollen Lymph Node In The Armpit?

Lymph nodes are small, bean-shaped structures that are found throughout the body. According to the Cleveland Clinic, they're connected by a network of lymphatic vessels, which transport a clear fluid called lymph throughout the body. As lymph flows through the lymph nodes, waste products are filtered to ensure the fluid is clean. This makes lymph nodes an important part of the immune system, since they play a vital role in defending the body against bacteria and other harmful substances.

According to the clinic, lymph nodes are found in many different parts of the body, including the neck, armpits, and groin. The armpit alone has more than 20 lymph nodes. It is a complex region that contains a number of important structures, including hair follicles (via WebMD). In addition to its function in the lymphatic and circulatory systems, the armpit area is home to a number of sweat glands. If you have swollen lymph nodes in the armpit area, there may be various causes. It's important to monitor them closely and keep track of how long the area remains swollen.

Causes of swollen lymph nodes in the armpit

According to Medical News Today, certain viral and bacterial infections can cause lymph nodes to swell. One example is cellulitis, which happens when bacteria penetrate the skin's deeper layers after a cut or injury. When an infection or other type of irritation occurs in the body, as part of the immune response, the lymph nodes in the area may work to fight off the infection. 

Lymph nodes contain immune cells called lymphocytes, which are responsible for identifying and attacking invading microorganisms and other foreign substances (via Physiopedia). The lymph nodes might then become swollen and tender to the touch after going into action, per Medical News Today.

According to Cleveland Clinic, mononucleosis can also cause lymph nodes to swell. Mononucleosis is a viral illness that is caused by the Epstein-Barr virus (EBV). It is characterized by symptoms such as fever, sore throat, swollen lymph nodes, and fatigue (per Mayo Clinic).

There are many other possible causes of swollen lymph nodes in the armpit, including allergies and autoimmune disorders, per Medical News Today.

When to see a doctor

It is not uncommon to have swollen lymph nodes from time to time, especially if you are fighting off an infection or other type of irritation. In most cases, swollen lymph nodes will go down once the underlying cause has been treated (via Cleveland Clinic). However, there are certain situations where it is important to see a doctor for swollen lymph nodes.

In some cases, swollen lymph nodes in the armpit may indicate cancer. According to Medical News Today, you should see a doctor if your lymph nodes are hard, fixed, or do not go down after several weeks. This is especially important if the swelling is accompanied by other symptoms such as fever, unexplained weight loss, or night sweats.

It is also important to see a doctor if you are concerned about the appearance or location of your swollen lymph nodes. Your doctor may perform a physical examination and may order additional tests, such as an imaging test to determine the cause of the swelling. Treatment will depend on the underlying cause of the swollen lymph nodes.