The armpit, medically known as the axilla, is a complex anatomical region that serves as a junction for numerous structures, including muscles, major blood vessels, nerve bundles, and lymph nodes. Experiencing pain in this area, often called axillary pain, is a common symptom that can be alarming due to the density of these underlying tissues. The causes of this discomfort are varied, ranging from temporary irritations to indications of a more serious systemic process. Understanding the specific location and nature of the pain is often the first step in determining whether the cause requires professional medical attention.
Common Causes Originating in the Skin and Muscles
Some of the most frequent sources of armpit discomfort arise from the skin itself or the surrounding muscle tissue. The warm, moist environment of the axilla makes it susceptible to various skin irritations, such as folliculitis, which is the inflammation of hair follicles, often triggered by shaving. Allergic contact dermatitis may also occur as a reaction to ingredients found in deodorants, antiperspirants, or laundry detergents, resulting in a painful, itchy rash.
Physical exertion is another common cause, leading to muscle strain in nearby structures like the pectoral muscles or the latissimus dorsi, which are involved in arm and shoulder movements. Activities such as heavy lifting, intense resistance training, or repetitive overhead motions can cause micro-tears in these fibers, resulting in pain that radiates into the armpit area. Less common but still originating in the skin is a chronic condition called hidradenitis suppurativa, which involves painful, deep-seated nodules and abscesses forming repeatedly in areas where skin rubs together.
Understanding Pain Related to Lymph Node Swelling
The axillary lymph nodes are a central component of the body’s lymphatic system, serving as filters to collect fluid, waste, and immune cells from the arm, chest wall, and breast. When an infection or foreign substance is detected, these nodes become active, producing infection-fighting cells, which causes them to swell and become tender. This swelling, known as lymphadenopathy, is the most common reason people experience a painful lump in the armpit.
Most often, this swelling is a benign response to a localized infection, like a cut on the arm, a skin infection, or a common respiratory illness such as a cold or the flu. Recent vaccinations, particularly those administered in the arm, can also stimulate the nearby axillary nodes, leading to temporary swelling and tenderness. The nodes typically decrease in size and tenderness as the underlying infection resolves, usually within a few weeks.
Systemic conditions can also trigger a widespread, prolonged swelling of the lymph nodes, including autoimmune disorders or generalized viral infections like mononucleosis. Persistent, painless, hard, or fixed lymph node swelling can be a sign of malignancy, such as breast cancer, lymphoma, or other cancers that have spread to the area. The axillary nodes are the primary drainage site for breast tissue, making them a common area for cancer cells to accumulate.
Pain Caused by Nearby Nerve or Breast Tissue Issues
Pain felt in the armpit can sometimes originate from structures outside the immediate axillary cavity, particularly nerves or breast tissue. The brachial plexus is a network of nerves originating in the neck and shoulder that passes through the armpit to supply the upper limb. Compression or irritation of these nerves, perhaps from carrying a heavy bag over the shoulder or specific sleeping positions, can cause sharp, radiating pain, numbness, or tingling in the axilla and down the arm.
A specific type of nerve pain, known as intercostobrachial neuralgia, can manifest as chronic burning or shooting pain in the armpit and inner arm, often following surgery in the chest or breast area. Breast tissue extends high up into the armpit, forming an area known as the Tail of Spence. Pain originating from this tissue is common, particularly in women, and is often related to hormonal fluctuations associated with the menstrual cycle, pregnancy, or fibrocystic breast changes. This hormonal tenderness can make the armpit feel swollen and painful.
Warning Signs and When to Seek Medical Care
While most armpit pain is temporary and resolves on its own, certain symptoms warrant a medical evaluation to rule out a more serious cause. Severe, sudden armpit pain accompanied by chest pressure, shortness of breath, or pain radiating down the left arm can be signs of a cardiac event. Signs of a severe infection, such as a high fever, a spreading area of redness, or red streaking extending from the armpit, require prompt attention.
If the pain or lump is persistent, it should be examined by a healthcare provider, especially if it does not subside within one to two weeks. Lumps that feel hard, are fixed in place, or continue to grow without an apparent cause like a cold or injury are concerning features that require investigation. Other systemic symptoms, including unexplained weight loss, night sweats, or persistent fatigue accompanying the armpit pain, indicate the need for a thorough medical assessment.