Swollen lymph nodes in the armpit usually feel like small, round lumps just under the skin that are tender to the touch. A normal armpit lymph node is less than 10 mm (about the size of a pea) and typically can’t be felt at all. When nodes swell, they become large enough to notice with your fingertips and may feel like a marble or grape beneath the surface.
Where Armpit Lymph Nodes Are Located
Your armpit contains roughly five clusters of lymph nodes spread across the area, not just one spot. The main group sits at the base and center of the armpit, embedded in the fatty tissue there. Others are tucked along the chest wall near the edge of the pectoral muscles, behind the armpit near the shoulder blade, alongside the main vein running through the area, and up near the top of the armpit close to the collarbone. In total, there can be 20 or more individual nodes in a single armpit.
This spread matters because swelling doesn’t always show up in the most obvious spot. A lump near the front of the armpit, right where the chest muscle meets the arm, is just as likely to be a lymph node as one deep in the center of the hollow.
How to Check Your Armpit for Swollen Nodes
Start by raising one arm slightly, then using the opposite hand to feel the armpit area. Use the pads of your fingers (not the tips) and press with gentle, circular motions. You want enough pressure to feel structures beneath the skin but not so much that you’re pushing past them. Work your way across the entire hollow of the armpit, from the chest wall in front to the back near your shoulder blade, and up toward the collarbone.
Keep your fingernails trimmed so you can press comfortably. The key technique is to compare both sides. Clinically significant lymph nodes are almost always asymmetric, meaning one side will feel noticeably different from the other. If both armpits feel roughly the same, what you’re feeling is more likely normal tissue. If one side has a distinct lump the other doesn’t, that’s worth paying attention to.
A swollen node typically feels like a smooth, rubbery ball that moves slightly when you press on it. It may be tender or painless. Nodes swollen from infection are often sore to the touch, while painless, hard, or fixed-in-place lumps are the ones that warrant faster medical attention.
What a Normal Node Feels Like vs. a Swollen One
A normal axillary lymph node measures under 10 mm in diameter. At that size, most people can’t feel them through the skin at all. Nodes in the armpit are generally considered insignificant if they stay under about 3 cm (roughly 1.2 inches), though context matters. A 2 cm node that appeared overnight with a fever is different from one that’s been the same size for years.
When checking, pay attention to a few characteristics beyond just size:
- Texture: Soft or rubbery nodes that move freely are more typical of infection or a normal reactive response. Hard, firm, or fixed nodes that don’t slide under your fingers are more concerning.
- Tenderness: Pain when you press on a node usually signals an active infection or inflammation, which is the most common cause of swelling.
- Shape: Normal and reactively swollen nodes tend to feel oval or bean-shaped. Irregularly shaped lumps deserve medical evaluation.
- Number: A single swollen node on one side is more notable than a few slightly enlarged ones on both sides during a cold or infection.
Common Causes of Armpit Swelling
The vast majority of swollen armpit lymph nodes are caused by infection. Your armpit nodes drain lymph fluid from your arm, chest wall, and breast tissue, so any infection in those areas can trigger swelling. Skin infections like cellulitis, wound infections, and even an infected cut on your hand or arm are frequent culprits. Cat scratch fever, caused by a bacterial infection from a cat scratch or bite, is a classic cause of isolated armpit node swelling.
Broader infections also cause armpit lymph node swelling. Mononucleosis, measles, and HIV can all enlarge nodes throughout the body, including the armpits. Even a bad case of strep throat or an ear infection can cause generalized node swelling that you notice most in the armpit because of how accessible the area is.
Vaccines are another very common and harmless cause. COVID-19 vaccines and other immunizations given in the upper arm frequently cause temporary swelling in the armpit lymph nodes on the same side as the injection. Current medical guidelines consider this a benign finding for up to 12 weeks after vaccination. If you’ve had a shot in that arm within the past three months, swelling on the same side is almost certainly a normal immune response and doesn’t need additional workup. After 12 weeks, persistent swelling should be evaluated.
Signs That Suggest Something More Serious
Swollen armpit nodes rarely indicate cancer, but certain patterns raise the level of concern. The risk factors for malignancy include being over 40, having nodes that are hard and painless, and noticing swelling that persists or grows over several weeks without an obvious cause like an infection or recent vaccine.
Systemic symptoms are the most important red flags to watch for alongside swollen nodes. These include unexplained weight loss of more than 10% of your body weight, drenching night sweats (not just feeling warm at night, but soaking through your clothes or sheets), and persistent fevers without an obvious infection. This combination of symptoms can point toward lymphoma or other serious conditions that need prompt evaluation.
Location also matters. Swollen nodes just above the collarbone (the supraclavicular area) are more concerning than those in the armpit itself. If you feel a lump in that higher region alongside armpit swelling, that’s a reason to get checked sooner rather than later.
What Happens During a Medical Evaluation
If you visit a doctor for a swollen armpit node, they’ll start with a physical exam and ask about recent infections, vaccines, skin injuries, and systemic symptoms. In many cases, especially when there’s an obvious infection, they’ll recommend watching the node for a few weeks to see if it shrinks on its own as the infection clears.
When further evaluation is needed, ultrasound is typically the first imaging tool used. It can measure the node precisely and assess its internal structure, including the thickness of the outer layer (the cortex), which helps distinguish reactive swelling from something more concerning. Normal cortex thickness is under 3 mm; areas of focal thickening beyond 6 mm are considered highly suspicious. If the ultrasound raises concerns, a needle biopsy may follow to sample the tissue directly.
Most swollen armpit lymph nodes resolve on their own within two to four weeks once the underlying cause, usually an infection, clears up. Nodes that persist beyond that window, continue to grow, or are accompanied by the systemic symptoms described above are the ones that typically get a more thorough workup.