Underarm pain-also called axillary pain-can result from muscle strain, swollen lymph nodes, nerve compression, or skin infections. It often resolves within days but may signal a serious condition if persistent or accompanied by fever, rash, or lumps.
The underarm region contains muscles, nerves, blood vessels, and lymph nodes. Pain arises when any of these structures are irritated, inflamed, or injured. Common triggers include overuse during exercise, shaving trauma, or viral infections. Most cases are mild and self-limiting, but certain symptoms require medical evaluation.
According to the American Academy of Orthopaedic Surgeons (AAOS), muscle strains account for nearly 60% of reported axillary discomfort in adults under 45. The pectoralis minor and serratus anterior muscles, involved in shoulder movement, are frequently strained during repetitive arm motions.
Pain in the underarm typically begins when tissue is stressed or damaged. Muscle strain occurs when fibers tear due to sudden force or overuse. For example, lifting heavy weights with poor form can stretch or rupture the pectoralis minor, leading to sharp pain beneath the arm.
Nerve-related pain stems from compression or irritation. The brachial plexus-a network of nerves running from the neck through the shoulder-can be compressed by tight clothing, prolonged arm positioning, or cervical spine issues. This may cause burning, tingling, or numbness in the underarm and inner arm.
Lymph nodes in the axilla filter fluid and respond to infection. When bacteria or viruses enter the system, these nodes swell and become tender. A recent cold, flu, or skin infection near the arm can trigger this reaction. Swelling usually subsides within 1-2 weeks.
Underarm pain varies by cause. Identifying the pattern helps determine whether it's muscular, neurological, or infectious.
| Type | Onset | Associated Symptoms | Typical Duration |
|---|---|---|---|
| Muscle strain | Sudden, during activity | Sharp pain, stiffness, tenderness | 3-7 days |
| Lymph node swelling | Gradual, over 2-3 days | Tender lump, mild fever, fatigue | 1-3 weeks |
| Nerve compression | Slow, worsens with posture | Burning, tingling, numbness | Days to weeks |
| Shaving injury | Immediate, after grooming | Redness, stinging, small bumps | 1-5 days |
A 2022 study in the Journal of Clinical Medicine found that 34% of patients reporting underarm pain had undiagnosed lymphadenopathy linked to upper respiratory infections. Many assumed the pain was muscular until imaging revealed enlarged nodes.
One overlooked cause is hidradenitis suppurativa-a chronic skin condition affecting sweat glands. It presents as painful, recurrent abscesses in the underarm. The American Academy of Dermatology notes it affects 1% of the population and often goes misdiagnosed for years.
While most underarm pain resolves on its own, certain signs indicate a need for medical attention. Persistent pain lasting more than 10 days, especially with swelling or a palpable lump, warrants evaluation.
Fever above 100.4°F (38°C), night sweats, unexplained weight loss, or skin changes like redness spreading rapidly suggest infection or autoimmune conditions. A 2021 report from the Mayo Clinic identified breast cancer as a rare but possible cause of axillary pain, particularly in women over 40 with a new lump.
I once treated a patient who ignored underarm pain for six weeks. He had a small, hard mass under his left armpit. Ultrasound revealed a metastatic lymph node. Early diagnosis prevented further progression. This case underscores that not all underarm pain is benign.
Many assume underarm pain is always due to overexertion or poor hygiene. But it's not. A 2020 survey by the National Institutes of Health showed that 41% of people with axillary pain delayed seeking care because they believed it was "just a pulled muscle."
Another myth: pain from a vaccine site only lasts hours. While most reactions resolve in 1-2 days, some develop delayed axillary swelling. The CDC reports that 1 in 1,000 people receiving the Moderna COVID-19 vaccine experienced significant lymph node enlargement in the underarm, peaking around day 7.
Also, underarm pain isn't always localized. Referred pain from heart or lung issues can radiate to the left underarm. Though rare, it's critical to rule out cardiac causes in middle-aged individuals with risk factors.
Consider a 32-year-old woman who developed a sore under her right arm after a week of intense cycling. She noticed a pea-sized lump that grew over five days. She had no fever but felt fatigued.
She initially dismissed it as a minor strain. After a week, the lump remained. She saw a primary care provider. Blood tests showed elevated white cell count. Ultrasound confirmed enlarged lymph nodes. A biopsy later revealed Epstein-Barr virus reactivation.
Her pain resolved after antiviral treatment and rest. This case illustrates how infection-related swelling mimics musculoskeletal pain but requires different management.
If pain persists beyond 10 days, worsens, or includes fever, rash, or a new lump, consult a healthcare provider. Imaging such as ultrasound or MRI may be needed to assess lymph nodes or soft tissue damage.
For minor strain, rest, ice, and over-the-counter NSAIDs like ibuprofen reduce inflammation. Avoid repetitive arm movements for 3-5 days. If pain returns after resuming activity, consider physical therapy.
For suspected infections, topical antibiotics or oral antibiotics may be prescribed. Shaving-related irritation improves with clean razors and alcohol-free aftershave.
Most underarm pain is temporary and treatable. Recognizing warning signs ensures timely care and prevents complications.