Causes of Armpit Pain and Treatment Options

There are many possible causes of armpit or underarm pain (referred to medically as axillary pain) that can range from mostly a nuisance to serious. Irritation from deodorant, infections in the sweat glands, injuries, nerve compression, or even cancer are only a few of the possibilities. Pain may occur alone or be associated with a rash, swollen lymph nodes, or other signs.

Diagnosis often begins with a careful history and physical exam, but blood tests and imaging tests may be needed to determine the cause and figure out the best treatment. Even when armpit pain is accompanied by enlarged lymph nodes in the axilla, breast cancer that has spread is not the most common cause.

Armpit Anatomy and Structure

Before talking about the potential causes of armpit pain and what your doctor may recommend to alleviate it, it's helpful to think about the anatomy of the underarm (axilla) and what structures "live" there.

Structures and tissues found in the armpit include:

• Muscles: Towards the back of the axilla are the teres major and latissimus dorsi muscles. The pectoralis major enters this region from the chest. The coracobrachialis runs centrally through the armpit and the arm muscles—including the deltoid, long head of the triceps, and biceps—are nearby.
• Blood vessels: Both veins and arteries travel through this region.
• Nerves: The brachial plexus lies just above the armpit, and the median, ulnar, radial, and musculocutaneous nerve all travel through this region.
• Sweat glands: There are many sweat glands in the armpit, which are responsible for the all-too-common underarm odor and not uncommon infections in this region.
• Lymph nodes: There are roughly 20 to 40 axillary lymph nodes in each armpit. These lymph nodes, in turn, receive drainage from lymph vessels in the arm, breast, and part of the neck, chest, and upper abdomen.
• Bones: Beneath the armpit sit the upper ribs and just above the armpit is the head of the humerus (upper bone of the arm), where it connects with the scapula (shoulder blade).
• Skin: There are a number of skin conditions that may affect the different layers of the skin. Within these layers are hair follicles, sweat glands, fat, connective tissue, and more.

The armpit is very warm relative to many parts of the body (one of the reasons why temperature was often taken in the armpit in the past), which, when combined with the overlap of tissues when the arms are hanging down against the body, makes this a place where infections can flourish.

Causes of Armpit Pain

There are a number of different causes of armpit pain. Pain can be caused directly, but conditions involving the structures in and near the armpit can be referred pain (pain that originates in a different part of the body from where it is felt) from more distant regions. Some causes may result in pain in only one armpit, whereas others (such as enlarged lymph nodes due to a viral infection) may result in pain on both sides.

Muscle Strain

The armpit muscles are subject to overuse and muscle strain, especially with activities such as lifting, pulling, throwing, or pushing. Activities such as lifting weights and playing sports (for example, baseball) can result in strains and sprains.

Local pressure on the muscles and other structures of the armpit, such as with the use of crutches, can also cause significant armpit pain.

Injuries

There are a number of ways in which the structures of the armpit may be injured, giving rise to pain. A network of nerves above the shoulder form the brachial plexus. Brachial plexus injuries may occur when an arm is forcefully pulled or flexed, and can lead to armpit pain, as well as loss of motion in the shoulder, weakness, and numbness or tingling in the hand or arm. Other injuries in this region, including shoulder dislocations, may cause pain in the axilla.

Skin Irritation and Rashes

The skin in the armpit can become irritated, leading to pain. Clothing that is tight under the arms and rough fabrics can be irritating. Irritation is also common with shaving. In addition, both irritant and allergic contact dermatitis can be caused by deodorants, soaps, lotions, laundry detergents, and more.

Other noninfectious rashes that may occur in the armpit (and cause discomfort) include acanthosis nigricans, a velvety rash often found in people who have diabetes or are obese, and psoriasis.

Hidradenitis suppurativa is a chronic condition involving sweat glands (usually in the armpit or groin) that is similar to severe acne. Treatment options can range from acne medications to antibiotics, immunomodulators, and sometimes surgery. Without treatment, boils (see below) may form, and fistulas between the infection and the surface of the skin may develop.

Infections

Both local and systemic (throughout the body) infections may lead to armpit pain. Some of these cause inflammation locally, and others affect the lymph nodes in the armpit, leading to pain.

Fungal infections, including yeast (candidiasis) are common. Intertrigo usually causes a very red, shiny rash with scaling in areas where skin touches skin, such as the armpit. Ringworm (tinea corporis) may occur anywhere on the body and often causes an itchy rash with red bumps in a circular pattern.

Several common bacterial skin infections may lead to pain in the armpit, often associated with redness or swelling. Erythrasma begins as a pink rash that turns brown and scaly and is commonly found in the armpit. Often confused with a fungal infection, erythrasma is caused by a bacteria known as Corynebacterium minutissimum. It is often linked with humidity and diabetes. Other infections such as cellulitis, folliculitis, furuncles (boils), and carbuncles may occur. When a boil is left untreated, it may develop into an abscess.

Some generalized infections can cause enlarged lymph nodes in the armpit (see below), leading to pain.

Enlarged Axillary Lymph Nodes

Pain in the armpit may be accompanied by swollen lymph nodes, though early on there may not be any obvious lumps or swelling. Lymph nodes in the armpit (axilla) may be enlarged for a number of reasons, with some causes being more common with enlargement on one side (unilateral axillary lymphadenopathy), and others affecting both armpits. Potential causes of enlarged axillary lymph nodes include:

• Infections: Viral infections such as infectious mononucleosis and HIV, bacterial infections such as cat scratch disease, syphilis, tuberculosis, and parasitic disease such as toxoplasmosis may lead to tender and enlarged axillary nodes (lymphadenitis). Infections in the breast (mastitis), hand, arm, neck, and parts of the chest and upper abdomen may also drain to the lymph nodes in the axilla, causing pain and swelling.
• Autoimmune disease: Conditions such as rheumatoid arthritis and lupus may lead to enlarged painful lymph nodes in the armpit.
• Cancer: There are a number of cancers that can spread to the axillary lymph nodes. Lymphomas (such as Hodgkin's lymphoma) may begin in these lymph nodes. While many people are familiar with the spread of breast cancer as a cause of lymph node metastases, almost any cancer may spread to these nodes, including lung cancer and melanoma. In some cases, enlargement and pain of a lymph node in one armpit may be the first sign of cancer.

Enlarged lymph nodes related to infection are often tender, soft, and mobile, compared with those from cancer often being non-tender, fixed, and firm, but there are many exceptions.

Nerve Compression

Compression of any of the nerves in the armpit (pinched nerves) may cause armpit pain that is often burning in nature. This may be accompanied by tingling or numbness in the hand or arm or weakness. Nerve compression may be caused by an injury or from pressure on the nerves as a result of a tumor or swelling. One type of lung cancer, Pancoast tumors, may cause pain in the armpit. This can be associated with swelling of the face, neck, or upper arms, and can easily be missed on a chest X-ray.

Shingles

Shingles is a condition that occurs when chickenpox reactivates in the nerve root, where it persists. In time, a rash usually develops along the area supplied by the nerve (dermatome), but at the onset, it's common to only have pain.

Benign Masses

In addition to cancerous (malignant) tumors, there are a number of benign tumors and conditions that may lead to armpit pain. This can include cysts, lipomas, and fibroadenomas.

Lymphedema

Lymphedema is a condition in which the normal flow of lymph is disrupted, often related to surgery for breast cancer. It can lead to a deep ache in the armpit, often accompanied by swelling of one arm.

Acid Reflux

Acid reflux can sometimes result in pain that is only felt in the armpit.

Heart Disease

We usually think of chest pain when we think of heart disease, but symptoms of coronary artery disease, especially heart disease in women, can be very nonspecific and vague, and may only include symptoms of pain in the armpit. The pain is usually dull and achy, and may be accompanied by discomfort in the back or jaw, nausea, and a general feeling that something is wrong.

Peripheral Arterial Disease (PAD)

Just as narrowing of the blood vessels of the heart can cause chest pain and heart attacks, narrowing of the major blood vessels supplying the arm (peripheral artery disease) can lead to pain that is felt in the armpit.

Menstrual Period Related Pain

Many women experience breast tenderness just before and during their menstrual periods that can radiate into the armpit, but some may experience this discomfort only in the armpit.

When to See a Doctor

Deciding when to see your doctor will depend on the severity of your pain, whether it is limiting your daily activities, associated symptoms, and much more.

If your symptoms are mild but persist, make an appointment to see your doctor. Pain is our body's way of telling us something is wrong.

Questions Your Doctor Will Ask

There are a number of questions your doctor may ask to help determine the source of your pain. These can include:

• The quality of the pain: Is it sharp or dull and achy, does it feel tingling or burning, or is it itchy in nature?
• The duration: When did the pain begin? Is it constant or intermittent? Is it getting worse?
• The intensity: How severe is the pain on a scale of 1 to 10, with 1 being barely there pain, and 10 being the worst pain you can imagine?
• What other symptoms are you having? For example, a fever or chills, night sweats, pain in other locations, or swollen lymph nodes in other locations?
• Have you had a rash, redness, or have you noted any other changes in your armpit?
• Have you had any scratches or cuts on your hand or arm?
• Have you started any new activities or sports?
• Have you had any type of injury recently?
• Have you used any new deodorants, lotions, bath soaps, or laundry detergents?
• If you are a woman, when was your last mammogram? Do you have a family history of breast cancer? Have you noted any breast lumps on examination?
• How much is the pain interfering with your daily life?

Diagnosis

To make a proper diagnosis of armpit pain and make sure you aren't missing anything subtle, it's important to see your doctor. They will take a careful history, including asking many of the questions above. They will then perform a physical exam. This will include looking for any redness, rashes, lumps, or enlarged lymph nodes in your axilla.

They will also examine the areas surrounding your armpit, such as your head and neck, arms, and chest, perform a neurological exam focusing on ruling out nerve compression, and perform a careful breast exam (even if you are a man, as men can get breast cancer also). Depending on what they find, further tests may be done.

Labs and Tests

If you have signs of an infection (either a local infection or a body-wide infection that could be causing enlarged lymph nodes), a complete blood count may be ordered.

Imaging

Imaging tests may also be needed. These could include an ultrasound, CT scan, MRI, or a PET scan if you have a history of cancer. A mammogram may also be recommended (or a breast MRI if you have a strong family history of breast cancer or very dense breasts).

Procedures

Imaging studies can suggest possible diagnoses, but a biopsy is needed to make an accurate diagnosis if cancer is suspected. If you have a large boil or abscess, an incision and drainage may be needed. In addition, seeking prompt medical attention at the onset of many of the causes listed above may reduce your risk of complications or worsening of the condition.

Treatment

The treatment of armpit pain will depend on the underlying cause.

If your pain is due to a muscle strain, ice, rest, and gentle movement may be recommended. If your armpit is irritated, avoiding whatever caused the problem will be advised. If lymph nodes are swollen due to a benign cause, warm compresses may be recommended.

No matter the cause, wearing clothes that fit loosely in the armpit, as well as avoiding shaving or using any lotions, creams, or deodorants in your underarm area may help reduce pain.

Prevention

Many causes of armpit pain can't be prevented, but some can. Being careful with personal care products may reduce your risk of irritation. Properly warming up before sports and avoiding overuse of your arm and shoulder are also wise.

A Word From Verywell

There are many potential causes of armpit pain, and though many people think of breast cancer, especially if an enlarged lymph node is present, the most common causes are muscle strain or irritation related to deodorants and other products. That said, armpit pain can sometimes be a sign of something more serious, and it's important to see your doctor to get an accurate diagnosis and treatment recommendations.