What are the Causes of an Armpit Lump?

Author: Mayda Asif  PT, DPT

Medical Reviewer: Azuka Chinweokwu Ezeike, MBBS, FWACS, FMCOG, MSc (PH)

Highlights

• Armpit lumps are mostly harmless and often come from infection, irritation, or benign growths.
• A hard lump, fixed or growing, or associated with fever, weight loss, or night sweats, needs immediate medical attention.
• Small lumps may go away on their own, but a lump that lasts should not be ignored.
• Good hygiene, gentle shaving, and early treatment of skin problems can help lower the risk of some lumps.
• Staying alert to warning signs and involvement of breast tissue can help you get the right diagnosis and treatment sooner.
• If a lump does not improve or grows rapidly, see a doctor promptly.

Introduction

Discovering an armpit lump during a shower or while you are getting dressed can be a surprise, but it might not always be something dangerous. 

Most of the time, an armpit lump is just a harmless swelling of glands, a cyst, a fat collection, or an ingrown hair follicle. However, it is important to get a check-up if the lump is hard, keeps growing, or feels stuck. Your doctor will perform a physical examination and use specialised tests to reach a correct diagnosis. [1]  

Usually, an armpit lump is a small bump or swelling that comes from normal body structures such as lymph nodes, sweat glands, or fat tissue. 

Your armpit or axilla is more than just skin and hair; it contains a collection of lymph nodes (bean-shaped organs that produce lymphatic fluid, which helps fight infection), sweat glands, fat, blood vessels, nerves, and sometimes a small amount of extra breast tissue. A lump can form from any of these structures. [2]

 Common Causes of Armpit Lumps

1. Swollen Lymph Nodes: 

It is the most common cause of an armpit lump, and it is most commonly linked to an active immune response to an ongoing inflammation in the body. It is not always a sign of any serious condition. For example, lymph nodes may swell due to cold, flu, minor infections, or after a routine vaccine, but eventually they shrink back to their original size. [2], [3]

2. Skin and Hair Problems

Many underarm bumps, lumps, or discomfort can come from hair and skin problems in the armpit area. Frequent use of sharp blades, scented deodorants, skin conditions like hidradenitis suppurativa and the use of hair removal creams can create ingrown hairs and boils, and irritate the skin's normal gradient. These appear as red, sore, or itchy patches in the armpit and can be mistaken for lumps. [4]

3. Cyst or Fatty Lumps: 

A cyst and a fatty lump may sound alarming, but it's not as dangerous as it sounds. 

• A cyst is a small, fluid-filled, round lump that exists just beneath the skin and has a very slow growth potential. It has a firm and slightly squishy feel. A cyst is completely harmless until it grows in size or becomes sore, red, and infected. 
• Lipomas are soft fatty lumps that are not cancerous. They have a soft, doughy feel and can easily move when pressed or felt. They take months and years to develop and rarely turn into something serious. IF lipomas are large and painful, your doctor might conduct a detailed examination. [5]

4. Hormonal and Immune System Triggers 

• Hormonal shift during menstruation, pregnancy, or breastfeeding can make the breast tissue under your arm feel fuller, lumpy, or sore. If the changes are more prominent on one side and do not resolve on their own, it is important to visit a doctor.  [6]
• In autoimmune conditions, like lupus and rheumatoid arthritis, the immune system becomes sensitive and creates swollen lymph nodes. [7] An overactive immune system can be coupled with fatigue, joint pain, rashes, and fever. So, the doctors usually conduct blood tests and imaging instead of treating the individual lump.

5. Rare but Serious Causes

In some exceptional cases, the lump might indicate a serious underlying problem. For instance:

Breast Cancer 

Very often, breast cancer first spreads into the lymph nodes of the armpit. So, in some cases, an armpit can in fact be a very first sign of cancer. 

This type of lump may feel like a single, firm, and hard area in the armpit, or a painful thickening that extends below to the breast tissue. They have an unusual feel that is entirely different from harmless cysts or lipomas. 

Lymphoma (Cancer of the Lymphocytes (White Blood Cells))

Lymphoma is a cancer of the lymph nodes, and since the armpit contains many lymph nodes, it can sometimes start here and present as swollen lymph nodes or a large lump in the armpit. 

The affected lymph node (s) can enlarge quickly and have a high growth potential. If you can see a rapidly growing lump or swelling in your armpit, it is recommended to see a doctor as soon as possible. 

When Should You Worry about Armpit Lumps?

You should worry about armpit lumps if they show up with certain ”red flags”, these are the signs that signal a serious health problem. [8]

1. How long it lasts and how it behaves

• An armpit lump that lasts more than 2-3 weeks and keeps getting worse without any apparent infection or body stressors. This type of lump is a typical presentation of lymphadenopathy, and a doctor visit should not be delayed. 
• If a lump is rapidly growing in days or weeks, it is far from normal and should be immediately evaluated. [8]

2. What does the Lump Feel like?

• If a lump is hard, firm, or fixed in its place and does not move when pressure is applied from the fingers, it is a red flag and should be checked accordingly. [8]
• A painless lump that keeps growing and does not shrink, as in a normal infection-and-repair cycle, should be properly evaluated by a doctor. [8]

3. Accompanying symptoms that raise concern 

Even if there are no other symptoms and a lump casually comes up with these signs, you should not hesitate to get it checked. 

1. Fever
2. Night sweats
3. Unexplained weight loss
4. General tiredness/fatigue
5. Skin changes

    4. Skin changes in the armpit and breast that should not be ignored 

If you see these changes in your breast, along with the armpit lumps, you must see a physician 

1. Redness 
2. Dimpling in the breast
3. Thickening of the skin
4. Nipple pulling in

    5. Long-standing Lumps 

A long-standing, painless lump that is fixed, keeps getting larger, and is coupled with breast changes, night sweats, fevers, and weight loss is a red flag and must be evaluated by a specialist. 

To rule out any serious conditions, your doctor will perform a detailed ultrasound and might go for a needle biopsy of the lump.   

How to Prevent Armpit Lumps 

Armpit lumps can not be completely prevented, because most of the causes (swollen lymph nodes, breast changes, cysts or lipomas) are a part of the normal body mechanism. 

However, you can lower the risk by 

• Shaving gently 
• Looking out for any follicles or 
• Skin problems and treating it early, 
• Keeping the armpit area clean. 
• Tracking your vaccines 
• Getting regular breast scans. 

How to Get Rid of Armpit Lumps?

Armpit lumps are diverse; some do not need any attention, while others require immediate care. Here are a few methods that can help you get rid of an armpit lump 

1. Watch and Wait: 

Small, soft and harmless lumps usually go on their own within a few weeks. A gentle and warm compress can help you ease any pain or discomfort. Keep in mind that if the lump starts growing rapidly and you experience any red flags, it's very important to see a doctor. 

2. Medical Treatment 

A medical treatment is always provided by a qualified professional, according to the needs of an individual. These are a few ways your doctor might approach the cause of your armpit lump.

1. Antibiotics are used if the lump is related to a bacterial infection
2. Anti-inflammatory or pain medication can be used as oral medicine or over-the-counter creams to reduce pain while the real problem resolves underneath. 
3. Drainage or minor surgeries are conducted for the removal of a cyst or abscess in the armpit area.
4. Your doctor might suggest hygiene changes if the lump is due to inappropriate shaving or the use of deodorants. 

Conclusion 

An armpit lump is harmless if it is a cyst, infection, irritation, or a benign growth. If the lump is hard, fixed or rapidly growing, and it is accompanied by fever, weight loss, and night sweats, it should be evaluated by a doctor. Many small lumps resolve on their own, but if a lump does not improve, it should not be ignored. Proper hygiene and early care can reduce the risk.. 

References 

[1] Donuru A, Obaid H, Al Attar M, Kandula V, Purnell D. Axillary lump: an unusual presentation of fat necrosis in the breast. Australas Radiol 2007;51 Spec No.:B40-42. https://doi.org/10.1111/j.1440-1673.2007.01820.x. 

[2] Yoshimoto N, Yanagi A, Takayama S, Sakamoto M, Tomoda K, Ishikawa K: Timing and Duration of Axillary Lymph Node Swelling After COVID-19 Vaccination: Japanese Case Report and Literature Review. In Vivo 2022;36:1333–6. https://doi.org/10.21873/invivo.12834. 

[3] Tu W, Gierada DS, Joe BN. COVID-19 Vaccination-Related Lymphadenopathy: What To Be Aware Of. Radiol Imaging Cancer 2021;3:e210038. https://doi.org/10.1148/rycan.2021210038.  

[4] Lauro W, Capasso G, Fabbrocini G, Marasca C. Hair removal and deodorants in hidradenitis suppurativa: An online survey on patients’ habits. J Cosmet Dermatol 2023;22:692–5. https://doi.org/10.1111/jocd.15373. 

[5] Deka RK, Gogoi B, Kumar N, Choudhury A. Giant Axillary Lipoma. Journal of Evolution of Medical and Dental Sciences 2017;6:1650. https://doi.org/10.14260/JEMDS/2017/362. 

[6] Ali AA, Faraj FH. Clinicopathological profile of mastalgia in females: incidence, types, and pathological correlations. a cross-sectional study. Ann Med Surg (Lond) 2023;85:4764–72. https://doi.org/10.1097/MS9.0000000000001159. 

[7] Shrestha D, Dhakal AK, KC SR, Shakya A, Shah SC, Shakya H. Systemic lupus erythematosus and granulomatous lymphadenopathy. BMC Pediatr 2013;13:179. https://doi.org/10.1186/1471-2431-13-179. 

[8] Sakthivel M, Krishnamoorthy Y, Sarveswaran G, Jayalakshmy R, Priyan S, Bharathnag N. Screening for red flag symptoms of cancer: A community-based cross-sectional study from urban Puducherry, India. J Edu Health Promot 2018;7:174. https://doi.org/10.4103/jehp.jehp_89_18. 

Disclaimer:
The information provided on this website is for general educational and informational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Published May 22, 2026