What’s Causing Your Painful Armpit Lumps?

Why is there a lump in your armpit?

A painful lump in the armpit may feel odd but it’s usually not too worrisome. It typically means one of two things: You have a skin infection or your lymph nodes are swollen.

With all the sweat, friction, bacteria, and irritation from shaving and clothing, the armpit is a ripe environment for skin conditions like cysts or ingrown hairs.

Additionally, there are networks of lymph nodes in this area, which can swell up when your body is trying to fight off an infection. Less commonly, lumps can be caused by chronic conditions, like autoimmune diseases or cancer.

If you have a painful armpit lump, you may also have:

• Armpit rash or bumps
• Armpit itch, burning, or pain
• Oozing pus
• Painful, swollen lymph nodes in multiple parts of the body

2. Boil (furuncle)

Symptoms

• Red or pink golf ball-size bump in your armpit
• Pain
• Oozing pus

A boil, or furuncle, is an infected hair follicle. Bacteria, usually Staphylococcus aureus (“staph”), can get into the hair follicle if there is open skin or irritation, which often happens after shaving.

Boils typically form in the armpit because it is a warm, moist, and dark area that bacteria can easily enter and grow. Bacteria from a razor blade can get into the skin and spread the infection.

It is important to treat the boil because the infection can spread and lead to cellulitis (skin infection). In rare cases, it can get into the bloodstream and cause a body wide infection (called sepsis).

Use warm compresses or hot-water soaks and allow the pus to drain. Your doctor may also cut and drain the boil and prescribe antibiotics. To prevent it from happening again, throw out your razors.

3. Skin abscess

Symptoms

• Red, fluid-filled bump ½ cm to 2 cm in diameter
• Bumps filled with pus
• Pain

A skin abscess is a large pocket of pus that has formed just beneath the skin. Usually, bacteria (Staphylococcus aureus) gets in from a small cut or scratch and multiplies under the skin. The body’s white blood cells fight the invasion, killing some of the bacteria, while also forming pus inside the cavity.

The body's immune system may heal a small abscess on its own. But your doctor may need to drain or lance the abscess to clean out the pus and prescribe antibiotics. This will help relieve the pain.

If an abscess is not treated, it can grow larger and spread the bacteria through the bloodstream, which can be dangerous. Fever, body aches, and chills can be signs that the infection has spread throughout your body.

4. Folliculitis

Symptoms

• Pink or red bumps around hair follicles
• Itch or pain
• Pus-filled bumps

Folliculitis is inflammation of the hair follicle. It occurs when bacteria (usually Staphylococcus aureus) gets into the hair follicle, causing inflammation and pus. The bacteria enters through open skin and can even live on an old razor. It can be very itchy or painful.

Often folliculitis will go away on its own. Your doctor may give you topical creams or oral antibiotics for more severe cases.

Throw away your razor blade if you have folliculitis. Changing your razor blade often can also help prevent it.

5. Ingrown hairs

Symptoms

• Pink or red bumps around hair follicles
• Itch or pain
• A hair in the center of the bump curled under the skin

Ingrown hairs occur when the hair itself grows back into the skin. The body sees it as a foreign object and reacts by sending inflammatory cells to the hair. This causes a red or pink bump around the hair, which can be very itchy or painful. Ingrown hairs often occur in people who have thick or coarse hair.

The treatment for ingrown hairs is to stop shaving for several days. Your doctor may prescribe a topical steroid lotion to calm inflammation or perform a quick in-office procedure to clip the hairs out of the bump, which prevents further inflammation. If you often get ingrown hairs, always shave in the direction of hair growth and use a new razor blade each time you shave.

6. Hidradenitis suppurativa

Symptoms

• Painful fluid-filled bumps, often the size of a golf ball
• Blackheads in the armpits
• Tunnels connecting the lumps, which may leak pus
• Additional bumps in the groin folds, under the breasts or buttocks

Hidradenitis suppurativa causes painful lumps to form under the skin. The lumps can become quite large and drain pus. When it’s chronic, it causes scarring and tunneling in the areas of the lumps and can be quite painful. The lumps can also develop in the groin folds or under the breasts or the buttocks.

No one knows the exact cause of Hidradenitis suppurativa, but it involves hair follicles that become inflamed and blocked. Genetics and hormones also play a role. Being overweight and smoking can make the condition worse. Since it is not contagious, you cannot spread it to others.

You may need topical medications, steroids injected into the bumps, or antibiotics that also act as anti-inflammatories, such as doxycycline. When the condition is severe, your doctor may prescribe oral or injectable medications that suppress your immune system. Or they may perform surgery to remove the bumps and repair the scarring/tunneling.

7. Enlarged lymph nodes

Symptoms

• Armpit lump
• Lumps that move under the skin

Lymph nodes are the glands in your body that contain the cells of the immune system. The lymph nodes filter out bacteria and viruses. When you have a virus, such as a cold or flu, or another infection, the lymph nodes drain your system and help fight the infection. When this happens, the lymph nodes swell, which can make them painful.

Enlarged, painful lymph nodes are usually caused by a viral infection or from a local bacterial infection on the skin near the lymph nodes. You may also have a fever, chills, muscle aches, or cough and congestion with the flu or virus.

In rare cases, they may be due to an autoimmune disease. Or the cause may be a mystery.

Enlarged lymph nodes can also be a sign of cancer. But when it’s from cancer, the lymph nodes are usually not painful.

Enlarged lymph nodes caused by infections go away on their own when the infection is gone. When the cause is cancer, the enlarged bump will not go away on its own.

See your doctor about any enlarged lymph node that does not go away in several weeks.

8. Mononucleosis

Symptoms

• Fatigue
• Headache
• Muscle aches
• Loss of appetite
• Cough
• Fever
• Rash
• Swelling in the neck and armpits

Infectious mononucleosis, also called "mono" or "kissing disease," is a viral infection caused by Epstein-Barr virus. It is spread through saliva or other body fluids and is very contagious. Teenagers and young adults are the most likely to get it. The virus causes fever, muscle aches, fatigue, and loss of appetite. The lymph nodes in the armpits and other areas may become enlarged.

Because mononucleosis is caused by a virus, antibiotics will not help. Treatment consists of bed rest, fluids, and good nutrition. It’s important to have your doctor monitor your condition and make sure there is no secondary bacterial infection or damage to the heart, liver, or spleen.

Other possible causes

A number of conditions can also cause painful armpit lumps, though these are either rare or painful armpit lumps are not usually the main symptom. They include:

• Cancers, such as lymphoma
• Rheumatoid arthritis
• Systemic lupus erythematosus
• Tuberculosis
• Lipomas
• Lymphangitis
• Kikuchi disease
• Rosai Dorfman disease
• Axillary granular parakeratosis

Should I go to the ER for painful armpit lumps?

Seek emergency treatment if you also have:

• Fever
• Chills
• Redness and warmth at the site of the lump
• Inability to eat or drink
• Inability to think clearly