Slight differences between the left and right sides of the human body, known as asymmetry, are common. This natural variation can extend to the armpits. Observing that one armpit appears larger than the other is often a normal aspect of bodily development and function.
Natural Asymmetry and Common Factors
Differences in armpit size often stem from benign physiological factors. Variations in muscle development are a frequent cause. Individuals who use one arm more extensively in daily activities or sports might develop slightly larger pectoral or latissimus dorsi muscles on that side, influencing the contour of the adjacent armpit. This muscular development can make one armpit appear more pronounced.
Fat distribution also plays a significant role. The body naturally stores fat unevenly, and the armpit area (axilla) can accumulate fat distinct from breast tissue. This asymmetry in fat deposition can be influenced by genetics, hormonal changes, and weight fluctuations. Poor posture can further accentuate these differences by causing skin folds that make one armpit appear larger.
When to Consult a Doctor
While many instances of armpit asymmetry are benign, certain signs warrant medical evaluation. Consult a healthcare provider if you observe a new lump or persistent swelling lasting longer than two weeks. Other concerning indicators include pain, redness, or warmth in the area, suggesting inflammation or infection. Changes in skin texture, such as dimpling or thickening, or any discharge should also prompt a medical visit.
Rapid changes in a lump’s size, or if it feels firm and fixed rather than movable, are important signs to discuss with a doctor. These symptoms necessitate professional assessment to determine the underlying cause and ensure appropriate management.
Potential Medical Explanations
A larger armpit, when accompanied by specific symptoms, can indicate various medical conditions. Swollen lymph nodes are a frequent cause, often signaling the body’s immune response to an infection in the arm or breast, or a systemic viral illness like mononucleosis or influenza. Lymph nodes, which are part of the immune system, can enlarge when filtering germs or abnormal cells. In some cases, persistent or significantly enlarged lymph nodes might point to more serious conditions, including certain types of cancers such as lymphoma.
Benign cysts can also contribute to armpit asymmetry. Epidermal cysts are non-cancerous sacs filled with keratin, which can form when hair follicles become blocked. Sebaceous cysts develop from damaged sebaceous glands and contain an oily substance called sebum. Both types typically present as round, movable lumps under the skin and may become tender or inflamed if infected.
Lipomas, which are soft, fatty tumors, are another common benign cause of lumps in the armpit. These growths consist of fat cells and are generally painless. Hidradenitis suppurativa, a chronic inflammatory skin condition, can cause painful, recurring lumps, cysts, and abscesses in areas where skin rubs together, including the armpits. This condition results from clogged hair follicles and can lead to the formation of tunnels under the skin.
Accessory breast tissue, also known as polymastia or supernumerary breasts, is a congenital variation where extra breast tissue develops outside the normal breast area, often in the armpit. This tissue can respond to hormonal changes, potentially becoming more noticeable or tender during puberty, menstrual cycles, or pregnancy, and may appear as a prominent lump or thickening in the armpit region.