What Causes Swollen Lymph Nodes in the Armpit?

The lymph nodes are small glands that are part of your immune system. They contain white blood cells and are responsible for filtering out harmful substances in the lymph fluid. Swollen lymph nodes (medically known as lymphadenopathy) can happen for several reasons. Infections, health conditions, and certain medications can all cause this reaction. 

Fortunately, many causes of swollen lymph nodes are treatable. Several infections can be treated with antibiotics, antivirals, or antifungals. Chronic health conditions like an autoimmune disorder or cancer are also treatable with medications or surgery. If your lymph nodes are swollen, meet with your healthcare provider to develop a treatment plan.

Bacterial Infections

When bacteria enter the body, they can cause a bacterial infection. When the lymph nodes detect harmful substances like bacteria, they react and become swollen. Several bacterial infections may be causing your symptoms, including the ones below.

Cellulitis 

Cellulitis is the most common bacterial skin infection and occurs when bacteria like group A Streptococcus enter deeper layers of skin. This infection can cause your skin to look red, swollen, and pitted (like the peel of an orange). Other symptoms include swollen lymph nodes, a fever, and chills.

Antibiotics can help improve symptoms. You can lower your risk of cellulitis by washing your hands often and keeping wounds clean, dry, and covered. 

Cat Scratch Disease

Cat scratch disease is a bacterial infection spread by cats that can occur when an infected cat licks a person’s open wound or bites or scratches to break the skin. This infection causes discolored or swollen skin, raised sores (lesions) that may contain pus, swollen lymph nodes, headaches, a fever, poor appetite, and fatigue. The lymph nodes closest to the scratch may feel painful, tender, and swollen.

The cause of cat scratch disease is a type of bacteria called Bartonella henselae. Up to 30% of cats carry this type of bacteria, and infected cats often have no symptoms. To lower your risk of cat scratch disease, never let your cat lick an open wound. If you experience a cat bite or scratch, wash the area with soap and water immediately. 

Lyme Disease

Lyme disease is a bacterial infection caused by the bacterium Borrelia burgdorferi, which spreads from an infected tick bite. People who live near the Northeast, Mid-Atlantic, Upper Midwest, and Pacific coast are at a higher risk of being exposed to infected ticks. Common symptoms of Lyme disease include rash, fever, headache, swollen lymph nodes, and fatigue.

When left untreated, Lyme disease may lead to heart, joint, and nervous system symptoms. These symptoms often start 3-30 days after a tick bite. 

Trichomycosis 

Trichomycosis is a bacterial infection of the underarm hairs, which causes irritation and discomfort in the armpit. Common symptoms of trichomycosis often include more sweat and a foul odor in the armpit. You may also notice that your sweat is yellow, red, or black. The underarm hair usually becomes thicker and more coarse as well. 

Trichomycosis is not contagious and can be treated with antibiotics and good hygiene.

Syphilis 

Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum. Symptoms of syphilis occur in stages. The first stage may cause sores or bumps on the penis, vagina, anus, rectum, lips, or mouth. As syphilis progresses, it may lead to swollen lymph nodes.

Syphilis is curable with antibiotics. 

Toxoplasmosis

Toxoplasmosis is an infection caused by Toxoplasma gondii, which can spread by consuming undercooked, contaminated meat and shellfish. You might also develop this infection by drinking contaminated water and coming into contact with cat feces.

Most people exposed to toxoplasmosis do not develop symptoms because the immune system fights the infection. If you experience symptoms, you may have swollen lymph nodes and flu-like symptoms.

Early treatment is necessary. A severe infection can lead to permanent damage to the brain, eyes, and other organs. 

Viral Infections

Like bacteria, many viruses cause swollen lymph nodes. This happens when the immune system recognizes the virus and fights the viral infection, which can cause a host of symptoms including swelling in the armpit's lymph nodes.

Mononucleosis

Infectious mononucleosis, commonly known as mono, is a contagious, viral infection. It typically spreads through contact with body fluids, especially saliva. This is why it is sometimes referred to as, “the kissing disease.” It can also be spread by sharing cups and utensils. 

Common symptoms of mono include fatigue, fever, sore throat, headache, body aches, and swollen lymph nodes in the neck and armpits. Symptoms usually start about 4-6 weeks after the infection begins. 

Antibiotics are not effective against mono. Most people get better with home remedies (like rest and nutritious foods) within two to four weeks—but symptoms may last several weeks to months. 

Influenza (The Flu)

Influenza is a viral respiratory illness that infects the nose, throat, and sometimes the lungs. The flu spreads through exposure to tiny droplets when a person sneezes, coughs, or talks. Symptoms usually include a fever, chills, cough, sore throat, runny nose, body aches, headache, fatigue, and swollen lymph nodes.

You can lower your risk of contracting the flu by receiving an annual flu shot, washing your hands frequently, and limiting contact with people with the flu. 

HIV

Human immunodeficiency virus (HIV) is a serious viral illness that destroys a type of white blood cell in your immune system that helps your body fight infections. HIV greatly raises the risk of serious infections and diseases and can spread through bodily fluids like semen, vaginal fluids, and blood.

Symptoms of HIV may include fever, chills, rash, night sweats, sore throat, body aches, fatigue, mouth sores, and swollen lymph nodes. Symptoms usually come and go for the first few weeks of illness.

When diagnosed early, you can manage HIV with antiviral medications. 

Shingles

Shingles is a viral infection caused by the varicella-zoster virus (VZV), the same virus that causes chickenpox. If you had chickenpox as a child, you can develop shingles as an adult. About 1 in 3 people in the United States will experience shingles at some time—and the risk tends to increase with age. However, getting the shingles vaccine can reduce your risk of the infection.

If you experience shingles, you may develop symptoms like pain, itchy skin, a painful and blister-like rash, fever, chills, headache, and swollen lymph nodes.

Shingles is treatable with antiviral medications like Zovirax (acyclovir). 

Hepatitis

Hepatitis refers to the inflammation of the liver. Viral hepatitis may be caused by hepatitis A, hepatitis B, or hepatitis C. Many people with hepatitis do not show signs of it—but if you do develop symptoms, they may include fever, fatigue, nausea, vomiting, loss of appetite, pain, dark urine, clay-colored stools, and swollen lymph nodes.

The infection may last weeks to months, but vaccines are available to prevent hepatitis from occurring. 

Medical Conditions

Health conditions like autoimmune disorders and certain types of cancer may cause swollen lymph nodes in the armpits. The treatment options for these causes depend on the underlying condition you have and the severity of your symptoms.

Cancer

Certain types of cancer affect the lymph nodes. Hodgkin lymphoma and non-Hodgkin lymphoma are cancers that start in the lymph nodes, while leukemia affects the blood cells and may eventually cause swollen lymph nodes. 

Other types of cancer may start in another area of the body and spread to the lymph nodes through the lymph fluid or blood. Cancers of the head, neck, and breast are most likely to spread to the lymph nodes in the armpits because of their proximity to your armpits.

It's important to seek care from a healthcare provider as soon as possible. The treatment plan for cancer depends on the type of cancer you have, how advanced it is, and the severity of your symptoms. Common treatment options for cancer typically include surgery, chemotherapy, radiation therapy, and immunotherapy. 

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune condition that causes the immune system to attack healthy cells in the joints, leading to inflammation. People with RA usually experience pain in the joints of the hands, wrists, or knees. Symptoms of RA often include pain, swelling, and stiffness in the joints. You may also notice fever, fatigue, weight loss, weakness, and swollen lymph nodes.

Medications can help reduce symptoms. 

Systemic Lupus Erythematosus 

Systemic lupus erythematosus, more commonly known as lupus, is a chronic autoimmune condition that occurs when the immune system attacks healthy tissues in the body. Lupus affects several organs and can cause inflammation and damage to the skin, joints, heart, lungs, kidneys, blood cells, or brain. Lupus symptoms can vary widely, including pain, fever, a rash, hair loss, sores, and swollen lymph nodes.

There is no cure for lupus but medications and lifestyle changes can help you manage the condition well. 

Other Potential Causes of Swollen Lymph Nodes

Several other factors can also contribute to the swelling in your lymph nodes. They may include vaccine reactions, medications, and injuries.

Vaccine Reaction

In very rare cases, a vaccine could cause a reaction affecting the lymph nodes One 2022 case study found that one person who received the COVID-19 vaccine experienced swelling in the lymph node in their armpit. The risk of this reaction may increase with subsequent (additional) vaccines. In this case study, the person experienced lymph node swelling after her third COVID-19 vaccine. 

Medication Side Effects

All medications have some side effects, but certain medications raise the risk of swelling in the lymph nodes in the armpits. These drugs include:

• Aloprim (allopurinol): Treats gout and kidney stones 
• Tenormin (atenolol): Treats high blood pressure and chest pain
• Capoten (captopril): Treats high blood pressure and heart failure
• Tegretol (carbamazepine): Treats seizures and bipolar disorder
• Apresoline (hydralazine): Treats high blood pressure
• Dilantin (phenytoin): Treats seizures 
• Mysoline (primidone): Treats seizure disorders 
• Daraprim (pyrimethamine): Treats toxoplasmosis 
• Cardioquin (quinidine): Treats irregular heartbeats (arrhythmias) 
• Clinoril (sulindac): Treats pain

Swollen lymph nodes can also be a side effect of certain drug classes that treat bacterial infection—such as Cephalosporins, Penicillins, and Sulfonamides.

Injury

Swelling in the armpit can sometimes be due to a muscle strain or injury. The muscles in and around the armpits could become sore after overusing them with lifting, pulling, throwing, or pushing motions. Injuries to the shoulder, such as a shoulder dislocation, can also lead to pain and swelling in the armpit. As the injury heals, the swelling typically goes away.

Ingrown Hair

Ingrown hairs in the armpits occur when your hair curls back into a shallow layer of the skin instead of growing outward. If you develop ingrown hair, you'll likely experience irritation, swelling, pain, bumps, and itching in the armpits.

If your ingrown hair becomes affected, it can develop into a condition called folliculitis, which may require antibiotics or antibacterial home remedies for treatment. 

How To Treat Swollen Lymph Nodes

There are several treatment options for swollen lymph nodes in the armpits, but your exact treatment plan will depend on what's causing your swelling. If you have swollen lymph nodes, see your healthcare provider for an accurate diagnosis and begin treatment if necessary.

During your appointment, your provider will perform a physical exam and ask questions about your medical history, recent symptoms, current medications, and family history. They may also order additional diagnostic tests such as blood tests, imaging studies, and lymph node biopsies. 

Once your provider learns the cause of your symptoms, treatment will depend on what's causing your swollen lymph nodes. Treatment options may include:

When to Contact a Healthcare Provider

It's normal to experience swollen lymph nodes if you have an infection. As you recover, your lymph node swelling should improve. However, if your swollen lymph nodes stick around even after you're feeling better, it's a good idea to see your healthcare provider. Contact your healthcare provider urgently if you have swollen lymph nodes alongside the following symptoms:

• Extreme fatigue
• Unintended weight loss
• Night sweats
• Weakness 

These symptoms may be a sign of a more serious condition, so it's important to get support right away to reduce the risk of potential complications.

A Quick Review

Lymph nodes are a part of your immune system and can become swollen if you've developed an infection, condition, or injury. There are several possible causes of swelling in your lymph nodes ranging from bacterial infections, viral infections, autoimmune disorders, cancer, and medication side effects.

Treatment will depend on the underlying cause of your symptoms, but medications, therapies, and home remedies can help reduce the swelling effectively.