Causes of Swollen Lymph Nodes Under the Arm: What You Need to Know
Swollen lymph nodes under the arm, also known as axillary lymphadenopathy, can be a sign of various underlying health conditions. While it's normal to have small, pea-sized lymph nodes in the armpit area that are usually not noticeable, sudden enlargement or tenderness may indicate an immune response to infection, inflammation, or more serious medical issues. To determine the root cause, healthcare providers often recommend imaging tests such as ultrasound to evaluate the size, shape, and structure of the lymph nodes.
Common Causes of Axillary Lymph Node Enlargement
The lymphatic system plays a crucial role in fighting infections and filtering harmful substances from the body. When the body detects a threat—such as bacteria, viruses, or abnormal cells—the nearby lymph nodes may swell as part of the immune response. In the case of the armpit, several factors can contribute to this swelling, with inflammation and malignancy being the two primary categories.
1. Infections and Inflammatory Conditions
Inflammation is the most frequent and generally least concerning cause of swollen lymph nodes under the arm. Common infections like folliculitis—an inflammation of hair follicles—can trigger localized immune activity. Bacterial or fungal infections in the arm, hand, or chest area may also lead to reactive lymph node enlargement. These nodes typically retain their normal oval shape and may increase in size from the usual 1 cm to around 1.5 or even 2 cm.
In most cases, inflammatory swelling is accompanied by other symptoms such as redness, warmth, tenderness, or mild fever. The good news is that these types of swellings are often temporary and resolve once the underlying infection is treated with antibiotics, antifungals, or proper wound care.
2. Tumors and Malignant Conditions
Although less common, cancerous growths represent a more serious potential cause of enlarged axillary lymph nodes. When malignant cells from breast cancer, lymphoma, or metastatic cancers spread into the lymphatic system, they can accumulate in the armpit nodes, causing them to become enlarged, hard, and sometimes fixed in place.
Unlike inflammation-related swelling, cancer-induced lymphadenopathy often lacks pain and may persist for weeks or months without improvement. In some cases, the nodes lose their typical shape and appear irregular or fused together on imaging scans. Early detection through clinical examination and diagnostic testing—including biopsy—is essential for effective treatment and better outcomes.
When to See a Doctor
If you notice a lump under your arm that lasts longer than two weeks, continues to grow, or is associated with unexplained weight loss, night sweats, or fatigue, it's important to consult a healthcare professional promptly. While most cases are benign and linked to minor infections, ruling out serious conditions ensures peace of mind and timely intervention if needed.
Diagnostic tools like ultrasound, blood tests, and sometimes fine-needle aspiration can help identify the exact cause. Treatment will depend entirely on the diagnosis—ranging from rest and antibiotics for infections to surgery, chemotherapy, or radiation for malignancies.
Understanding the causes behind swollen lymph nodes under the arm empowers individuals to take proactive steps toward better health. By paying attention to changes in your body and seeking medical advice when necessary, you support early detection and effective management of any underlying condition.