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13 Causes of Armpit Lumps in Men

An illustration within a mustard yellow circle of a man's right armpit and shoulder with his arm raised. His skin is light peach-toned, and there are two lighter large lumps in his armpit, surrounded by grey medium length armpit hair. Four red lines come from the lumps.
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Last updated April 1, 2024

Armpit lumps quiz

Take a quiz to find out what's causing your lumps.

Found an intriguing armpit lump on yourself? Let’s get to the bottom of what may have caused the appearance of this abnormal mass.

8 most common cause(s)

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Enlarged lymph nodes
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Skin Abscess
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Hidradenitis suppurativa
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Cat-scratch disease
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An armpit lump is an abnormal mass of tissue that can arise from a variety of causes, ranging from not-so-serious to pretty-darn-serious. Although an armpit lump can develop in both men and women, several causes of armpit lumps are specific to men.

An armpit lump in men can appear as a bump or swelling, can be small or large, hard or soft, painful or painless. These lumps may be singular or several; likewise, they may develop under one arm or both. Armpit lumps in men, besides the medical problem they may present, also can cause day-to-day difficulties. Depending on the size or location of the lump, these problems can include arm or shoulder range of motion loss, painful arm positions, increased sensitivity to antiperspirants, deodorants or soaps or reduced clothing choices.

Let's explore some of the most common causes of armpit lumps in men, from the lowest risk types to the highest.

Low risk causes of armpit lump

Allergy to Vaccinations or Certain Medications

Some men may react to a vaccination, such as a flu shot, by developing a small underarm bump caused by a swollen lymph node. These bumps usually are not serious. However, if the bump persists or other symptoms such as fever develop, contact your physician to make sure that the bump is not the result of an infection rather than the vaccination. Similarly, some men may develop an armpit lump soon after starting a new medication. If this is the case, consult with your doctor to see if it would be possible to switch to medications.

Muscle Knot

Muscle knots can sometimes be the explanation for armpit swelling or lumps in men. These can result from overexertion or over-exercise and usually resolve on their own without medical attention. If necessary, rest and a break from exercise will speed healing. However, if the swelling or lump persists, a call to your doctor is wise.


A lipoma is a non-cancerous, slow-growing fatty lump that can occur in the armpit. Although sometimes unsightly, typically harmless. Most are rather small (less than 2 inches in diameter), feel firm or rubbery, and be easily moved with your fingers. Their cause remains unknown. Lipomas may become a problem if they begin to press on nearby nerves and cause pain. If their appearance bothers you or if they cause pain that hinders your day-to-day activities, there is a surgical option you can pursue.

Folliculitis (inflamed hair follicle)

Folliculitis occurs when an underarm hair follicle (the tiny base of a hair that lies below the skin's surface) becomes inflamed from an ingrown hair. This usually occurs as a result of shaving or irritation from close-fitting clothing. The resulting armpit bump is usually small, painful or tender and may itch or burn.

Most mild cases can be treated with warm, moist compresses several times a day. Cleaning the area gently with antibacterial soap also can help, as can application of over-the-counter antibiotic cream. If the lump does not disappear after a few days, your doctor may prescribe an antibiotic or antifungal medication.

Hidradenitis Suppurativa

Although uncommon, men can develop armpit lumps from this condition due to clogged sweat glands and blocked and inflamed hair follicles. The cause for the blockage remains unknown, but it is not an infection. Genetics, hormones, smoking, excess weight or a compromised immune system are thought to be causes. Small, tender, pimple-sized bumps can appear and may grow deeper into the skin, becoming quite painful, hard lumps that can be quite itchy. Sometimes, these lumps can link together under the skin by forming tunnels that can leak pus. Healing scars can form in the area, at times interfering with arm movement. If the underarm lumps do not resolve in a few weeks, a visit to your doctor is indicated.

Medium risk causes of armpit lump


Armpit lumps in men may result from pus-filled pockets under the skin that are painful, tender and often feel warm to the touch. Most commonly called boils (furuncles) they develop around a hair follicle and involve the nearby tissue. Sometimes boils connect to each other under the skin to form a network of abscesses called carbuncles. Abscesses usually can be treated with warm compresses, but if they persist or if fever develops, you should notify your doctor. The abscess may need to be cut and drained and an antibiotic prescribed.

Cat-Scratch Disease

This is an infection caused by the bacterium Bartonella henselae that may infect cats, although most cats show no signs of illness. Men can develop a painful armpit lump from this infection if they are bitten or scratched in this area by an infected cat or bit by its infected fleas. The underarm lymph node closest to the site can swell, turn reddish and/or warm. Fever, headache, fatigue and poor appetite can also occur. Usually, cat-scratch disease is not serious and requires no medical treatment. However, it symptoms persist, a doctor-prescribed antibiotic may be necessary.


Some infections can affect the entire body; lumps in one or both armpits may be the result. Infectious mononucleosis, most commonly caused by the Epstein-Barr virus, is one of them. HIV-AIDS, measles, mumps, chicken pox (varicella), shingles (herpes zoster) also can cause armpit lumps to appear in some men. If you suspect you may have one of these infections, it is necessary to consult your doctor for proper treatment.

Castelman Disease (giant lymph node hyperplasia, angiofollicular lymph node hyperplasia)

This is a seldom-seen, non-cancerous disease of the lymph nodes and related tissues that involves a severe overgrowth of lymphatic system cells (which help fight disease). Men with this condition will develop enlarged underarm lymph nodes (as well as the groin, neck and collarbone) in addition to appetite and weight loss, fever, night sweats, fatigue and an enlarged liver or spleen. Treatment usually consists of chemotherapy or radiation therapy.

Lymphadenitis (swollen lymph nodes)

One or more lumps in one or both armpits can be a sign of swollen lymph nodes (also called lymph glands) in men. Fortunately, swollen lymph nodes rarely are cancerous. Lymph nodes are an important part of the body's immune system and play an important role in fighting infection. The underarm lymph nodes are small and firm. When they become infected, it's usually due to an infection that began somewhere else in the body, either by a virus, bacteria or fungus. They then become enlarged and may be painful or tender to the touch. Swelling can be small—about the size of a pea—or large. Other symptoms may also emerge, such as runny nose, fever, night sweats, sore throat or fatigue. It all depends on the type of infection you may have. Although some armpit lumps due to swollen lymph nodes may resolve on their own within a few days, it's best to contact your doctor if you have any other these other symptoms. You should also see you doctor if these lumps appeared for no reason, continue to enlarge, have been present for at least two weeks, are immovable or feel hard or rubbery.

High risk causes of armpit lump


Acute lymphocytic leukemia (a cancer of the white blood cells) affects the lymphoid cells (a type of white blood cell), which help the body's immune system. When this type of cancer spreads to the lymph nodes in the underarm, lumps may result. Your doctor needs to be consulted immediately if you suspect you may have this condition.


Lymphoma is a cancer of the cells of the lymphatic system, which helps the body to fight disease. There are many types of lymphoma but the main subtypes are Hodgkin's lymphoma (HL) and non-Hodgkin's lymphoma (NHL). Both types can cause painless armpit lumps in men. The lump is usually hard and unmovable.

Often, such a lump is the first symptom of either type that men may experience. Other symptoms include fever, night sweats, fatigue and weight loss.

Breast Cancer

Although many people don't realize it, it is possible for a man to develop breast cancer. Both females and males have breast tissue. And breast cancer is a malignancy that develops from breast tissue cells. Although uncommon in men, breast cancer can develop. Unfortunately, most men do not consider breast cancer as a potential disease development for them. Breast cancer cells can enter the lymphatic system and spread to nearby lymph nodes, particularly those in the armpit. For some men, a painless, immoveable armpit lump is the first indication that they have developed this malignancy. If you develop such a lump that does not disappear, it's best to consult your doctor for further investigation.

Surprising possibilities: genital herpes

Genital herpes is a common sexually transmitted disease (STD) caused by one of the herpes simplex viruses—either HSV-1 (which can produce those annoying cold sores or fever blisters around your mouth) or HSV-2. Sexual contact with an infected person is the primary way in which the disease is spread. However, newborn babies can acquire herpes if the mother has already been infected.

More than one out of six people in the United States between ages 14 and 49 have genital herpes. It's estimated that over 775,000 people acquire new herpes infections each year. And most people are unaware that they may be infected with the virus because of the lack of symptoms or very mild symptoms. Herpes symptoms occur not only soon after the initial transmission of the infection but also throughout the person's life. The most common symptoms include small blisters around the genitals, rectum or mouth. These blisters can break and cause painful ulcers that then scab over. The initial herpes outbreak can also include body aches, fever, headache and swollen lymph nodes. These swollen lymph nodes usually occur in the genital area, but some people do experience swollen lymph nodes in one or both of their armpits.

So, how could genital herpes trigger armpit lumps?

Lymph nodes (some people call them lymph glands) are small, bean-shaped organs throughout the body. They're part of the lymph system, which transports lymph fluid, nutrients and waste matter between body tissues and the bloodstream. Groups of lymph nodes are found in the armpits, neck and groin. Some people with genital herpes experience a lump in either one or both armpits. It may or may not be painful or it may be tender to the touch. Some of the other herpes symptoms may be present as well but it's possible that the armpit lump may be the only sign. A warm, wet compress and over-the-counter pain relievers can help lessen the pain. If the armpit lump persists, it's best to contact your doctor; a prescription antiviral medication can help relieve symptoms. Untreated herpes infections (particularly those with genital sores) can increase the risk of acquiring other STDs, bladder infection and proctitis (rectal inflammation). Although rare, herpes infections can lead to meningitis, an inflammation of the membranes and cerebrospinal fluid surrounding the brain and spinal cord.

Here are some over the counter treatment that might help:

  • For Allergies: An antihistamine can reduce allergic reactions that might be causing swelling.
  • For Infections like Folliculitis: Antibacterial creams can help fight infection and reduce swelling.
  • For Pain and Swelling: Ibuprofen or acetaminophen can ease discomfort.
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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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