Lymph nodes are small, bean-shaped glands that are a central component of the body’s immune system, acting as filters for harmful substances and containing immune cells that fight infections and diseases. They are distributed throughout the body, with a significant cluster located in the armpit region, known as the axillary lymph nodes. When these lymph nodes become enlarged or swollen, it often indicates they are actively working to combat an issue within the body.
Infectious Agents
Swollen armpit lymph nodes frequently signal the body’s response to an infection, as immune cells proliferate within the nodes to combat invading pathogens. Bacterial infections are common culprits, with conditions such as cellulitis or abscesses in the arm or breast area often causing the adjacent axillary nodes to swell. For instance, bacteria like Staphylococcus or Streptococcus can trigger such a response when they cause skin infections. Cat scratch disease, caused by Bartonella henselae bacteria transmitted through a scratch or bite from an infected cat, is another bacterial cause.
Viral infections also commonly lead to swollen axillary lymph nodes as the immune system mounts a defense. Mononucleosis, caused by the Epstein-Barr virus, is a well-known example that can lead to generalized lymph node swelling, including in the armpits. Other widespread viral illnesses like the common cold, influenza, measles, mumps, and rubella can also prompt this immune reaction. If a shingles rash (herpes zoster) develops on the arm or upper torso near the armpit, the regional lymph nodes may swell in response to the viral activity.
Less frequently, fungal and parasitic infections can also contribute to axillary lymph node enlargement, especially in certain geographic areas or in individuals with weakened immune systems. Fungal infections like sporotrichosis, which can occur after skin exposure to contaminated soil or plant matter, may cause regional lymph node swelling. These infection-related swellings are often accompanied by other signs of inflammation, such as pain, redness, warmth over the affected area, or systemic symptoms like fever and general malaise.
Inflammatory and Immune Reactions
Beyond direct infections, swollen armpit lymph nodes can arise from various non-infectious inflammatory processes or immune system responses. Autoimmune diseases, where the immune system mistakenly attacks the body’s own healthy tissues, can cause generalized lymph node enlargement, including in the axillary region. Conditions such as rheumatoid arthritis or systemic lupus erythematosus exemplify how chronic inflammation throughout the body can activate the lymphatic system.
Allergic reactions can also provoke a response in the lymph nodes, particularly severe reactions to medications, insect bites, or other allergens. For example, a reaction to a drug might cause widespread inflammation, prompting the lymph nodes to become active. Localized skin irritations or minor injuries in the armpit area are another common cause for temporary swelling.
Simple irritations from shaving, certain deodorants or antiperspirants, small cuts, or insect bites can trigger a localized inflammatory response. The lymph nodes in the immediate vicinity activate to process the inflammation and prevent potential infection from these minor traumas. Recent vaccinations administered in the arm, such as the flu shot, COVID-19 vaccine, or tetanus shot, frequently lead to temporary swelling in the corresponding armpit lymph nodes. This swelling is a normal and expected sign that the immune system is building protection against the vaccine’s components.
Cancers
Swollen armpit lymph nodes can, in some instances, indicate the presence of cancer, a less common but more serious cause that requires prompt medical attention. Lymphoma is a type of cancer that originates directly within the lymphatic system, causing the lymph nodes themselves to become cancerous. This condition can manifest as either Hodgkin’s lymphoma or Non-Hodgkin’s lymphoma, both of which involve the uncontrolled growth of lymphocytes, leading to enlarged nodes. These cancerous nodes are often painless, which can sometimes delay detection.
Certain types of leukemia, which are cancers of the blood-forming tissues, can also lead to lymph node enlargement. While leukemia primarily affects the bone marrow and blood, the abnormal white blood cells can accumulate in lymph nodes, causing them to swell. The presence of enlarged nodes in leukemia might be accompanied by other systemic symptoms.
A significant cause of swollen axillary lymph nodes is the spread of cancer from other parts of the body, a process known as metastasis. The axillary lymph nodes are a common site for metastatic cancer, particularly from breast cancer, due to their proximity and role in draining lymphatic fluid from the breast. Melanoma, a serious form of skin cancer, and sometimes lung cancer, can also spread to these nodes, as the lymph nodes act as filters, trapping cancer cells that have broken away from the primary tumor. Cancerous lymph nodes often possess distinct characteristics, such as being firm, fixed in place (not easily movable), and persistent over time. They may also be accompanied by systemic symptoms like unexplained weight loss, night sweats, or persistent fever.
When to Seek Medical Guidance
It is important to seek medical guidance if you notice swollen armpit lymph nodes, especially if certain characteristics are present. If the swelling persists for longer than two to four weeks, a medical evaluation is warranted to determine the underlying cause. Nodes that are notably large, generally exceeding 1-2 centimeters, or those that are rapidly growing in size or increasing in number, should also prompt a visit to a healthcare professional.
Further indicators that suggest a need for medical consultation include lymph nodes that feel hard, firm, or fixed in place, rather than soft and movable. While many swollen nodes are painful, a painless, persistent lump can sometimes be more concerning. Accompanying symptoms such as unexplained weight loss, drenching night sweats, a persistent fever without an obvious cause, or unusual fatigue also necessitate medical investigation. Additionally, if there is no clear reason for the swelling, such as a recent infection, injury, or vaccination, professional advice should be sought.