What could be the reasons for a swollen right armpit?

Reviewed by Yoshinori Abe, MD

Internal Medicine

A swollen right armpit is often caused by enlarged lymph nodes, infections (bacterial, viral, or fungal), injury, allergic reactions, or skin conditions like cysts and boils. Less commonly, it may signal underlying issues such as autoimmune disorders or, rarely, certain cancers like lymphoma or breast cancer. Symptoms can include tenderness, redness, warmth, or a visible lump. Persistent, painful, or worsening swelling should be medically evaluated to determine the underlying cause and appropriate treatment.

Because armpit swelling can stem from anything as minor as irritation to something requiring prompt medical attention, understanding the likely cause early is important. Take a free, instant, online symptom check to get personalized insights based on your specific symptoms and clear guidance on what steps to take next.

Reviewed for medical accuracy: 07/15/2026

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Explanation

Swelling in the right armpit may be due to:

Swollen lymph nodes: Often caused by infections nearby, such as skin infections, respiratory illnesses, or after vaccinations. Infections: Abscesses or boils in the armpit area can cause swelling, redness, and tenderness. Injury or irritation: Shaving, deodorants, or friction can sometimes cause swelling or inflammation. Cysts or lumps: Noncancerous cysts or lipomas can cause localized swelling. Cancer: In rare cases, swollen lymph nodes from lymphoma or breast cancer can cause armpit swelling. Allergic reactions: To antiperspirants, soaps, or insect bites in the area.

If the swelling lasts more than a week, is painful, growing, or associated with other symptoms like fever or unexplained weight loss, you can use our free symptom checker to help identify potential causes and determine if you need medical evaluation.

(References)

Görkem SB, & O'Connell AM. (2012). Abnormal axillary lymph nodes on negative mammograms. Diagnostic and interventional radiology (Ankara, Turkey), 22415745.
de Andrade JM, Marana HR, Sarmento Filho JM, Murta EF, Velludo MA, & Bighetti S. (1996). Differential diagnosis of axillary masses. Tumori, 9061072.
Donuru A, Obaid H, Al Attar M, Kandula V, & Purnell D. (2007). Axillary lump: an unusual presentation of fat necrosis in the .... Australasian radiology, 17875154.

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