What could cause a swollen lymph node in the right armpit?

Reviewed by Yoshinori Abe, MD

Internal Medicine

A swollen lymph node in the right armpit is most often caused by infections (such as skin infections, colds, or viral illnesses), immune system responses, or reactions to vaccinations. Less commonly, it may signal conditions like lymphoma or breast cancer. Medical evaluation is recommended if the swelling persists longer than two weeks, grows larger, feels hard, or is accompanied by fever, night sweats, unexplained weight loss, or pain.

Because a swollen armpit lymph node can point to causes ranging from harmless infections to serious illness, understanding your specific symptoms is the critical first step. Rather than guessing or worrying, take a free, instant, online symptom check to identify likely causes based on your unique situation and get clear guidance on whether to monitor at home or seek medical care right away.

Reviewed for medical accuracy: 07/15/2026

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Explanation

Lymph nodes in the armpit help filter bacteria, viruses, and other harmful substances. Swelling occurs when they are active or irritated. Common causes include:

Infections: Such as skin infections, respiratory infections, or infections near the arm or breast. Immune responses: Reaction to vaccines or minor injuries. Localized inflammation: Due to irritation or allergic reactions in the nearby area. Cancers: Less commonly, swollen lymph nodes can be due to lymphoma or breast cancer. Other causes: Autoimmune diseases like lupus or rheumatoid arthritis.

If the swollen lymph node lasts more than 2 weeks, grows, becomes hard or fixed, or is accompanied by unexplained weight loss, night sweats, or fever, it's important to see a healthcare provider. You can also use a free symptom checker to better understand your symptoms and determine if medical attention is needed.

(References)

Görkem SB, & O'Connell AM. (2012). Abnormal axillary lymph nodes on negative mammograms. Diagnostic and interventional radiology (Ankara, Turkey), 22415745.
Hermansyah D, Al Anas M, Firsty NN, & Alianto R. (2022). Cat-Scratch Lymphadenitis Presenting with Right Upper .... Medical archives (Sarajevo, Bosnia and Herzegovina), 36937617.
Fujii T, Kimura M, Yanagita Y, Koida T, & Kuwano H. (2003). Tuberculosis of axillary lymph nodes with primary breast .... Breast cancer (Tokyo, Japan), 12736574.

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