Have you ever noticed a lump or swelling in your armpit and wondered what it could be? You’re not alone. Armpit swelling is a relatively common concern and can happen to anyone—often catching people off guard while showering, applying deodorant, or checking for other issues.
In this article, we’ll walk you through what armpit swelling means, what causes it, when to worry, and what tests or treatments may be needed. We’ll keep it simple, relatable, and informative.
What is Armpit Swelling?
Armpit swelling refers to a lump, bump, or enlargement in the area under your arm (the axilla). This swelling can be small and barely noticeable, or it might be tender, painful, or even visibly obvious. It may appear suddenly or develop slowly over time.
One of the most common reasons for armpit swelling is enlarged lymph nodes, which are small, bean-shaped structures that play a role in your immune system. The armpit is home to a cluster of these lymph nodes—so it’s no surprise they often get involved when your body’s fighting something off.
How Does Armpit Swelling Happen?
Let’s break this down simply.
Your lymph nodes act like security guards, filtering harmful substances like bacteria, viruses, and abnormal cells. When they detect a threat, they “call for reinforcements”—and that results in swelling as they fill up with immune cells and fluid. Think of it as a neighbourhood watch system getting activated.
But not all armpit swellings are due to lymph nodes. Sometimes, the swelling could come from skin infections, cysts, or even deeper issues like a tumour.
What Causes Armpit Swelling?
There are several possible causes for armpit swelling. Here’s a breakdown of the most common ones:
1. Infections (most common)
- Bacterial infections (e.g., boils or abscesses) – may come with redness, warmth, and pus.
- Viral infections (like the flu or mononucleosis) – lymph nodes swell as your immune system fights off the virus.
- Fungal infections – often seen in warm, sweaty areas.
- Vaccinations – like the COVID-19 or flu vaccine, can cause temporary swelling in nearby lymph nodes.
🔎 In fact, if doctors can confirm the swelling is an infected or reactive lymph node (based on clinical exam), no further tests may be needed initially.
2. Skin Conditions
- Ingrown hair
- Blocked sweat glands
- Cysts (like sebaceous or epidermoid cysts) – usually painless, dome-shaped lumps.
- Lipoma
3. Autoimmune Diseases
- Lupus or rheumatoid arthritis – these cause widespread inflammation and can lead to lymph node enlargement.
4. Cancers (less common but serious)
- Lymphoma – a cancer of the lymphatic system.
- Breast cancer – may spread to armpit nodes before being noticed in the breast.
- Leukaemia – can cause multiple lymph node enlargements, often painless.
- Melanoma or skin cancers – particularly if located near the armpit.
🧠 In one study, over 80% of armpit swellings in young adults were reactive (due to infection or inflammation). Only a small percentage—less than 5%—were due to cancer.
Who’s Most at Risk?
Armpit swelling can affect anyone, but some people are more likely to experience it:
- Teens and young adults – more prone to infections, cysts, and shaving-related irritation.
- People with weakened immune systems
- Those with recent vaccinations
- Individuals with a history of cancer
- People who use antiperspirants heavily or shave frequently
Other Symptoms That May Appear
Swelling often doesn’t come alone. Here are some symptoms that might tag along:
Common symptoms:
- Tenderness or pain in the armpit
- Redness or warmth over the lump
- Fever or chills if an infection is present
- Fatigue (in case of viral or systemic illness)
Concerning signs (see a doctor):
- Painless lump that doesn’t go away
- Growing in size over weeks
- Hard or fixed lump
- Accompanied by weight loss, night sweats, or persistent fatigue
Tests to Identify the Cause
If the swelling doesn’t go away within 1–2 weeks, or if it has worrying features, your doctor might order tests to get to the root cause. Here’s how they usually go about it:
Clinical Examination
- First step: Your doctor will feel the lump—checking size, texture, mobility, and tenderness.
- If it feels like an infected lymph node and you also have signs of infection, no further testing is needed immediately—you’ll likely be prescribed antibiotics and asked to come back in a week.
Further Tests (if necessary):
- Ultrasound of the armpit – painless and quick; helps see inside the lump.
- Blood tests – to check for infection, immune issues, or cancer markers.
- Fine Needle Aspiration (FNA) – to sample cells from the lump.
- Mammogram or breast ultrasound – if breast-related causes are suspected.
- CT scan or MRI – if deeper problems are suspected.
How is Armpit Swelling Treated?
Treatment depends on what’s causing the swelling.
1. Infections
- Antibiotics (if bacterial)
- Warm compresses and drainage (for abscesses)
- Swelling from viruses usually improves on its own.
2. Skin cysts or blocked glands
- Might need minor surgery or drainage
- Some resolve without treatment
3. Autoimmune causes
- Managed with medications like steroids or immunosuppressants
4. Cancer
- Treatment may involve surgery, chemotherapy, radiation, or targeted therapy—depending on the type and stage.
⚠️ Important: If the lump is hard, doesn’t move, or continues growing after a few weeks—get it checked, even if it’s not painful.
Final Thoughts
Most armpit swellings are harmless and temporary—especially if they show up after an infection or vaccination. But don’t ignore one that sticks around, grows, or feels unusual.
Listening to your body is the first step toward taking care of it. And in most cases, early detection leads to better outcomes.
References
- “Lymphadenopathy: Differential Diagnosis and Evaluation”, American Family Physician, 2011. https://www.aafp.org/pubs/afp/issues/2011/1015/p748.html
- “Axillary Swelling and the Differential Diagnosis”, Cleveland Clinic Journal of Medicine, 2018.https://www.ccjm.org/content/85/3/232
- CDC: Understanding Lymph Nodes and Vaccines, Centers for Disease Control and Prevention, 2021.https://www.cdc.gov/coronavirus/2019-ncov/vaccines/expect/after.html