What would cause pain under my left armpit and how can it be treated?

There are a few different reasons you might feel pain under your left armpit. One possibility is an axillary lipoma, which is a soft lump made of fat. Sometimes this lipoma can press on nearby tissues and even cause a condition called Complex Regional Pain Syndrome, where the pain spreads or feels stronger. Another cause could be an injury to the axillary nerve, which is a nerve that runs through the armpit. This type of injury can make the area hurt and may come from trauma or sometimes surgery. Swollen lymph nodes, or adenopathy, can also be the culprit; these nodes might swell when your body is fighting off an infection or inflammation, and this can cause discomfort. Treatment will depend on the cause. For a lipoma causing nerve pain, a doctor might recommend removing it or managing pain with medications. Nerve injuries often benefit from rest and physical therapy, sometimes along with pain relievers. If swollen lymph nodes are to blame, treating the underlying infection or inflammation will help. If the pain continues or gets worse, you can start by using our free AI symptom checker to help identify possible causes, then see a doctor who can check the area and suggest the best treatment plan.