Swollen lymph nodes in the armpit, medically known as axillary lymphadenopathy, are common, especially for new mothers. Many women notice these changes postpartum, particularly while breastfeeding. This often raises questions about the cause and whether it indicates a serious issue. Understanding the body’s immune responses and physiological changes during lactation can clarify why this occurs.
The Lymphatic System and Its Role
The lymphatic system is a complex network of vessels, tissues, and organs that plays an integral role in the body’s immune defenses. Lymph nodes are small, bean-shaped glands located throughout this system, with significant clusters found in areas such as the neck, groin, and armpits. These nodes function as filters, trapping foreign substances like bacteria, viruses, and damaged cells before they can circulate widely.
Inside the lymph nodes, specialized white blood cells, called lymphocytes, work to identify and destroy harmful invaders. When the body encounters an infection or inflammation, these immune cells multiply rapidly, causing the lymph nodes to enlarge and become noticeable. This swelling is a sign that the immune system is actively responding to a perceived threat or change within the body.
Breastfeeding and Lymph Node Swelling
During breastfeeding, the breasts undergo significant physiological changes that directly influence the axillary lymph nodes. Breast tissue extends into the armpit, so any breast activity or issue can affect nearby lymph nodes. Increased metabolic activity and blood flow to the breasts during lactation are normal processes that can lead to temporary enlargement of these nodes.
A common cause for swollen armpit lymph nodes in breastfeeding individuals is breast engorgement, which occurs when breasts become overly full of milk. This can lead to temporary swelling and discomfort, resolving as milk flow regulates. If a milk duct blocks, it can cause inflammation and potentially lead to mastitis, a breast tissue infection. Mastitis symptoms include localized pain, redness, warmth, flu-like symptoms, and can cause adjacent armpit lymph nodes to swell and become tender.
Minor infections, such as nipple thrush (a yeast infection), or bacteria from the infant’s mouth during feeding, can also trigger a localized immune response in the breast area. The lymph nodes then filter these substances, leading to their enlargement. These causes resolve as the underlying condition improves or as the body adjusts to lactation.
Other Potential Causes of Armpit Lymph Node Swelling
While breastfeeding can cause swollen armpit lymph nodes, many other factors also lead to this symptom. Infections are a frequent cause, ranging from viral illnesses like the flu, mononucleosis, or herpes, to bacterial infections such as strep throat, cellulitis, or cat scratch fever. These infections prompt the immune system to activate, causing nearby lymph nodes to swell as they filter pathogens.
Vaccinations, particularly those administered in the arm (e.g., COVID-19 or flu shots), can cause temporary lymph node swelling in the vaccinated armpit. This is a normal immune response as the body produces antibodies. Injuries to the arm or hand can also result in localized lymph node enlargement as the body responds to trauma and inflammation. Autoimmune disorders, including lupus or rheumatoid arthritis, can also lead to generalized or localized lymph node swelling as the immune system becomes overactive.
Swollen lymph nodes can indicate more serious conditions, including cancer. Lymphoma, a cancer originating in the lymphatic system, can cause painless lymph node enlargement. Cancers that begin elsewhere, such as breast cancer, can spread to the axillary lymph nodes, causing them to swell. A swollen lymph node is a symptom, not a diagnosis; its cause requires careful evaluation.
When to Consult a Healthcare Professional
While many instances of swollen armpit lymph nodes, especially during breastfeeding, are harmless and temporary, certain characteristics warrant medical attention. Consult a healthcare professional if swelling persists for more than two to four weeks or continues to increase in size. A doctor should also evaluate nodes that feel hard, rubbery, or fixed in place, rather than soft and movable.
Seek medical advice if the swollen lymph node is painless, as painful nodes are more commonly associated with infections. Accompanying symptoms such as unexplained fever, night sweats, significant unexplained weight loss, or persistent fatigue require evaluation. Any changes in the breast tissue itself, such as new lumps, skin dimpling, or nipple discharge, alongside swollen lymph nodes, also require medical assessment to rule out more serious conditions.