What Causes Swollen Lymph Nodes in the Right Armpit?

Swollen lymph nodes in the right armpit can be a sign of various underlying health conditions, ranging from mild infections to more serious diseases. While swollen lymph nodes are often the body's natural response to infection, persistent or unexplained swelling should never be ignored. The most common causes include infections such as mastitis and folliculitis, as well as more severe conditions like breast cancer and inflammatory breast cancer.

Common Causes of Right-Side Armpit Lymph Node Enlargement

1. Mastitis on the Right Side

Mastitis, particularly in breastfeeding women, is a frequent cause of swollen lymph nodes under the right arm. This condition occurs when breast tissue becomes inflamed, often due to a bacterial infection. If left untreated, it may progress into a breast abscess, triggering the immune system to activate nearby lymph nodes. As a result, the lymph nodes in the right armpit may become tender, enlarged, and warm to the touch. Prompt treatment with antibiotics and proper drainage, if necessary, typically resolves the issue.

2. Folliculitis in the Armpit Area

Folliculitis refers to an infection or inflammation of hair follicles, which can easily occur in areas prone to friction, sweat, and shaving—like the armpits. When bacteria such as Staphylococcus aureus invade the follicles on the right side, localized infection develops. This activates the regional lymphatic system, leading to noticeable swelling in the corresponding armpit lymph nodes. Maintaining good hygiene, avoiding tight clothing, and using antiseptic treatments usually help manage this condition effectively.

3. Breast Cancer Involvement

One of the more concerning reasons for swollen right armpit lymph nodes is the spread (metastasis) of breast cancer. Since lymph nodes act as filters for harmful substances, cancer cells from a tumor in the right breast can travel through the lymphatic system and accumulate in the nearby axillary (armpit) lymph nodes. This often makes the nodes firm, non-tender, and fixed in place. Early detection through clinical exams, mammograms, ultrasounds, and biopsies is crucial for improving outcomes and guiding appropriate treatment plans.

4. Inflammatory Breast Cancer (IBC)

Inflammatory breast cancer is a rare but aggressive form of breast cancer that can develop rapidly, especially during or after pregnancy. Unlike typical tumors, IBC often doesn't present as a distinct lump. Instead, it causes redness, warmth, swelling, and a pitted appearance of the skin—similar to an orange peel. Because of its fast-growing nature, it frequently leads to swift enlargement of the axillary lymph nodes. Given its high malignancy and tendency to spread quickly, immediate medical evaluation and advanced imaging are essential.

When to Seek Medical Attention

If swelling persists beyond two weeks, worsens over time, or is accompanied by other symptoms such as fever, unexplained weight loss, night sweats, or changes in breast texture, it's important to consult a healthcare provider. Initial anti-inflammatory treatments may be tried for suspected infections, but lack of improvement should raise red flags.

Recommended Diagnostic Steps

A thorough physical examination is usually the first step. Your doctor may order a breast ultrasound to assess any abnormalities in the breast tissue or lymph nodes. For further evaluation, especially when cancer is suspected, additional tests such as a diagnostic mammogram, MRI, or even a CT scan of the chest may be recommended. In some cases, a fine-needle aspiration or biopsy of the affected lymph node may be necessary to confirm the diagnosis.