Pain in the left armpit can be a perplexing symptom. This area contains a complex network of muscles, nerves, blood vessels, and lymph nodes. While many causes are benign and temporary, some may indicate a more significant underlying issue.
Muscle Strains and Skin Irritations
Pain in the armpit can stem from muscle strains in the surrounding areas. The pectoralis muscles, latissimus dorsi, and coracobrachialis all connect near the armpit. Overstretching or tearing these muscle fibers, often due to activities like lifting weights, sports, or repetitive movements, can cause pain that radiates into the armpit. This pain improves with rest and may be accompanied by tenderness or swelling.
The skin in the armpit is susceptible to irritations due to its warm, moist environment and frequent friction. Common culprits include razor burn, which can inflame hair follicles (folliculitis) or lead to ingrown hairs. Allergic reactions to deodorants, antiperspirants, soaps, or laundry detergents can cause contact dermatitis, resulting in itching, burning, redness, and a rash. Fungal infections like ringworm, which thrive in damp conditions, may also cause painful, discolored, and scaling skin.
Swollen Lymph Nodes
The armpits house a cluster of lymph nodes, known as axillary lymph nodes, which are part of the body’s immune system. These small, bean-shaped structures filter lymph fluid and trap foreign substances like bacteria and viruses. When the body fights an infection, these lymph nodes can swell as they produce more white blood cells, leading to pain and tenderness in the armpit.
Common infections causing swollen armpit lymph nodes include viral illnesses like the common cold, flu, or mononucleosis, and bacterial infections from a cut or bite on the arm or hand. Cat scratch disease, caused by bacteria from a cat scratch or bite, is another cause of localized lymph node swelling. While swollen lymph nodes are often a sign of infection, persistent or unusually hard swelling can warrant further investigation, as they can be associated with conditions like lymphoma or the spread of breast cancer.
Breast-Related Pain
Breast tissue naturally extends into the armpit area, sometimes referred to as the Tail of Spence. This anatomical connection means that conditions affecting the breast can manifest as pain in the armpit. Hormonal fluctuations, such as those occurring before menstruation, during pregnancy, or around menopause, can lead to fibrocystic changes, causing breast tissue to feel lumpy and tender, with pain sometimes radiating into the armpit.
Fluid-filled sacs known as breast cysts can also develop, causing localized pain or tenderness that extends to the armpit. For individuals who are breastfeeding, an infection of the breast tissue called mastitis can lead to inflammation and pain that may also be felt in the armpit. Although less common, armpit pain can be a symptom of breast cancer, especially if accompanied by a new lump in the breast or armpit, skin changes, or nipple abnormalities.
Nerve Issues and Other Systemic Causes
Armpit pain can arise from nerve involvement. Nerve compression, where a nerve is squeezed or entrapped, can cause pain, numbness, or tingling. Conditions like thoracic outlet syndrome, involving compression of nerves or blood vessels between the collarbone and first rib, may lead to armpit pain. Nerve inflammation, such as that caused by the varicella-zoster virus (the virus responsible for chickenpox), can also result in armpit pain before a characteristic rash of shingles appears.
Pain radiating to the left armpit can be a symptom of conditions affecting the heart, particularly if it occurs alongside other cardiac symptoms. Angina, which is chest pain due to reduced blood flow to the heart muscle, can cause discomfort that spreads to the left armpit, shoulder, neck, or jaw. A heart attack can also present with pain in the left arm or armpit, often accompanied by chest pain, shortness of breath, sweating, or dizziness. While isolated armpit pain is unlikely to be a sign of a heart issue, its presence with these other symptoms warrants immediate medical attention.
When to Consult a Doctor
While many causes of armpit pain are temporary and resolve on their own, some signs indicate the need for medical evaluation. Consult a healthcare provider if the pain is severe, worsens, or does not improve within a few weeks. Accompanying symptoms such as fever, persistent redness, warmth, pus, or the development of a new lump in the armpit or breast, should prompt a doctor’s visit. If armpit pain occurs with chest tightness, shortness of breath, dizziness, or pain radiating to the jaw or back, immediate medical attention is necessary.