The pain felt in the armpit, or axilla, is a common experience ranging from minor irritation to a sign of a deeper issue. This area is a complex junction, housing sweat glands, hair follicles, lymph nodes, and muscles connecting the chest, shoulder, and arm. Understanding this intricate anatomy helps explain why discomfort here is frequent and why the sensation can vary widely, from a surface burn to a deep ache.
Skin Irritation and Glandular Issues
The armpit surface is prone to superficial pain due to friction, moisture, and hair growth. Mechanical irritation, such as from shaving or constant rubbing, can cause a painful, red rash known as razor burn or chafing. This localized discomfort is typically visible and often accompanied by a burning sensation.
Contact dermatitis occurs when the skin reacts to a foreign substance, such as fragrances or chemicals found in deodorants, antiperspirants, soaps, or laundry detergents. The reaction causes inflammation, redness, and sometimes small blisters or intense itching, which can lead to pain when the area is moved or touched. Folliculitis, where a hair follicle becomes inflamed, often presents as small, tender, pus-filled bumps.
A chronic inflammatory condition is Hidradenitis Suppurativa (HS), which affects the apocrine sweat glands and hair follicles, typically in the armpits and groin. HS causes painful, deep-seated lumps that resemble boils or large pimples, which may rupture and drain pus. Recurring lesions can lead to the formation of tunnels beneath the skin and scarring, causing long-term pain and tenderness.
Swelling of Lymph Nodes and Infections
The armpit contains a concentrated cluster of axillary lymph nodes, which filter the body’s immune defense. These small, bean-shaped structures trap waste, bacteria, and pathogens from the fluid draining from the arm and chest wall. When the body fights an infection, the lymph nodes swell and become tender, a condition known as lymphadenopathy, causing deep, noticeable pain.
Common infections like a cold, flu, strep throat, or a localized skin infection can trigger this immune response, causing the nodes to enlarge. Swollen lymph nodes typically feel deep, firm, and movable beneath the skin, differentiating their pain from superficial skin irritation. They can remain slightly enlarged for a few weeks, even after the infection has resolved.
A localized, painful infection within the skin tissue itself, such as a boil or an abscess, can also cause significant armpit pain. This involves a collection of pus that develops deeper than folliculitis, often feeling like a hot, tender, deep lump that is not a lymph node. While most lymphadenopathy is a temporary response to infection or vaccination, persistent, unexplained swelling is a symptom that requires professional evaluation.
Muscle Strain and Nerve Compression
Pain in the armpit may be referred from nearby muscles or nerves. The axilla is a passageway for large chest and shoulder muscles susceptible to strain from physical activity. Overexertion from weightlifting, throwing motions, or new exercise routines can cause microscopic tears, resulting in a dull or sharp ache that radiates into the armpit.
This muscle pain is often exacerbated by movement, such as raising the arm, and is typically not associated with visible lumps or skin changes. The pain is usually a sign of tissue inflammation from overuse or injury and may be accompanied by stiffness or weakness. Rest and anti-inflammatory measures often help alleviate this musculoskeletal discomfort over several days.
Nerve irritation or compression can also cause pain that is mistakenly localized to the armpit. The brachial plexus, a network of nerves controlling movement and sensation in the arm and hand, passes through this region. Compression on these nerves, sometimes associated with conditions like Thoracic Outlet Syndrome, can cause sharp, shooting pain, tingling, or numbness that feels like it is radiating from the armpit down the arm.
Critical Symptoms Requiring Medical Review
While many causes of armpit pain are minor and self-resolving, certain symptoms signal the need for medical review. Severe pain that interferes with the ability to move the arm or perform daily activities should prompt a consultation. Pain accompanied by systemic signs of infection, such as unexplained fever, body aches, or chills, suggests a widespread process that needs treatment.
Specific changes in the armpit are also concerning, particularly if a lump is present. A lump that is hard, fixed in place, or does not move easily when touched, especially if it persists for longer than two weeks, should be evaluated by a healthcare provider. Rapidly worsening redness, swelling, or warm skin over a large area, or the development of a rash that does not improve, requires professional medical attention.