18 Common Causes of Pain in Left Armpit

The armpit is one of the sensitive parts of the body. Numerous blood vessels and nerves run through the armpits. Besides, your armpits are close to the breasts, and you may think you have developed breast cancer.

Luckily, most pains in the left armpit are not life-threatening and do not require medical help. But there are also cases you feel a sharp and shooting pain in your armpit area, which may be a sign of a severe health condition.

Many causes can lead to pain in the left armpit. For example, Muscle strain, Lymphadenitis, Angina, Hidradenitis Suppurativa, Sporotrichosis, Cancer, heartburn, Shingles, Anxiety, Infection, Pleurisy, Injury, Pinched Nerve or Cyst, etc. Here are some of the common causes.

Causes of Pain in Left Armpit
Causes of Pain in Left Armpit

18 Common Causes of Pain in the Left Armpit

1. Muscle Strain

The overuse or injury of the chest or arm muscles may lead to pain in the armpit. The pectoralis is a large chest muscle that runs up to the shoulders. This muscle can be injured by lifting weights or sports. The coracobrachialis, a muscle in the upper arm, can be damaged or strained from throwing activities or sports, such as tennis, weapon, and baseball.

If the chest or upper arm muscles become inflamed or sprained, you may feel pain in the left armpit or both.

Read: Causes of Pain under Left Rib Cage

2. Lymphadenitis (Lymph nodes inflammation)

Lymph nodes are oval-shaped organs that contain immune cells. These are responsible for attacking and killing unwanted contaminants or invaders, such as viruses. Lymph nodes are found in many body parts, such as the groin, neck, and armpits.

When you are sick or infected by a virus, the lymph nodes release disease-fighting cells and compounds. They may also become painful or inflamed. Inflamed lymph nodes are called lymphadenitis.

Your doctor may advise you to take a fever-reducing painkiller and warm compress. You can also alleviate the inflammation by elevating the affected area. Antibiotics can also help in fighting the infection that leads to inflammation.

If the lymph nodes are infected, an abscess may form. Your doctor will drain the abscess to alleviate the swelling. The treatment may include surgery, radiation, and chemotherapy if the lymphadenitis is due to a cancerous tumor.

3. Pain in Left Armpit Caused by Angina


Angina is chest pain due to reduced blood flow to the heart muscles. The blood carries oxygen, which the heart needs to function correctly. When the heart is deprived of oxygenated blood, it also leads to ischemia.

Angina is a symptom of coronary artery disease commonly described as pressure, tightness, heaviness, or pain in the chest. Other symptoms of angina may include:

  • Shortness of breath
  • Dizziness, nausea
  • Fatigue
  • Pain in arms, shoulder, neck, jaw, or back with chest pain
  • Chest pain

People who smoke, with diabetes, high blood pressure, high blood cholesterol, lack of exercise, a history of heart disease, and stress have a higher risk of developing angina if they are experiencing pain in the left armpit and chest get medical help immediately.

4. Hidradenitis Suppurativa

Hidradenitis Suppurativa is a skin condition that comes with sore lumps. It usually develops where the skin rubs together, such as the groin, buttocks, armpits, and under the breast. The tiny lumps may break, smell, and create tunnels under the skin.

This condition may occur when the hair follicles are inflamed or blocked. Many factors can cause blockages, such as hormones, genetics, metabolic syndrome, irregular immune system response, excess weight, and smoking.

The signs and symptoms may include:

  • Blackheads
  • Red Bumps
  • Pea-sized lumps
  • Tunnels

Early diagnosis and treatment can control the symptoms and avert further complications, such as infection, scars, limited movement, obstructed lymph drainage, social isolation, and cancer.

Read: Different Types of Pain on Left Side, Causes and Treatment

5. Sporotrichosis

Sporotrichosis, or rose handler’s disease, is an infection caused by a fungus (Sporothrix Schenck). This fungus is related to mold or yeast. Sporotrichosis is commonly linked with scrapes or cuts when handling vegetation (wood, moss, hay, sphagnum moss, sharp-stemmed plant, and soil). The infection is common among farmers, gardeners, and nursery workers. When mold spores enter the skin, it may take days or months to develop.

The first symptom of this condition is a bump or nodule on the skin. The color may range from pink to purple. It is usually tender and mild but may develop an open sore (ulcer) that drains clear liquid. Without proper treatment, the nodule and ulcer can be severe.

It may also spread to the arms and legs and last for years. In severe cases, the infection may spread to joints, bones, lungs, or the brain. If you think you or someone you know might have Sporotrichosis, seek medical attention for proper diagnosis and treatment.

6. Breast Cancer

Breast cancer forms in the breast cells and may occur in both men and women. The cause of breast cancer is not apparent, but a lifestyle, environmental factors, and hormones may increase the risk of breast cancer.

It often starts with cells in the milk-producing ducts or may begin in the breast’s glandular tissue or other tissue or cells. The signs and symptoms of breast cancer may include:

  • Breast lump
  • Change in shape, size, or appearance
  • Skin changes or scaling, flaking and peeling around the nipple
  • Suddenly inverted nipple
  • Redness or pitting of the skin

To diagnose breast cancer, tests and procedures may include a breast exam, mammogram, breast ultrasound, biopsy, and breast MRI. See a doctor immediately for early treatment if you are experiencing any signs and symptoms of breast cancer.

7. Heartburn or Acid Reflux

Heart Attack
Heart Attack

Another cause that can result in pain in the left armpit is heartburn. It is a burning sensation in the chest area behind the breastbone. The pain is usually worse when bending over or lying down. It occurs when the stomach acid backs up into the esophagus (a tube that transfers food from mouth to stomach). Heartburn that affects your daily tasks can sign a more severe condition that requires medical attention.

The symptoms of heartburn include:

  • Pain that worsens when bending over or lying down.
  • Chest pain that occurs after eating or at night.

If you are experiencing severe chest pain accompanied by other symptoms such as pain in the armpit, arm, jaw, or shortness of breath, seek medical help immediately.

Read:10 Common Causes of Sharp Pain Under Right Breast

8. Shingles near the Armpit

Singles are viral infections that may occur in any part of the body. It looks like a single stripe of blisters wrapped around the torso’s right or left side. If there is an eruption near the armpit, it can cause armpit pain. Shingles are caused by the same virus (varicella-zoster virus) that causes chickenpox. The signs and symptoms of shingles may include:

  • Pain, burning, numbness, or tingling sensation
  • Sensitivity
  • Red rashes
  • Itchiness
  • Fluid-filled blisters that break open

A person with shingles may also experience a headache, fever, fatigue, and sensitivity to light. Seek immediate medical help if the rash or pain occurs near your eyes, if you are 70 or above, if you have a weak immune system due to illnesses, or if the rash is painful and already spreading.

9. Anxiety

Anxiety is also associated with underarm pain. It results in shaking, sweating, irritation, and rapid heart rate, which may cause pain in the underarms. People with anxiety disorders often have intense, persistent, and excessive worry about daily circumstances. These feelings and panic can affect your daily tasks. Other signs and symptoms of anxiety may include:

  • Trembling
  • Difficulty controlling worry
  • Hyperventilation or rapid breathing
  • Feeling tense or nervous
  • Feeling tired or weak
  • Difficulty sleeping
  • Having the urge to avoid things that trigger anxiety
  • Gastrointestinal problems

See a doctor if you think you are worrying too much and it hinders your tasks, relationship, or other activities if you feel depressed and cannot control alcohol, drug intake, or suicidal thoughts.

10. Armpit Infection

Bacterial infections can result in fever, odor, and sore armpits. The condition could be caused by granular bacteriosis, trichomycosis axillaris, or folliculitis. If you find red splotches, lumps, and itchy spots, your pain in the left armpit could be caused by infected hair follicles or sweat glands. The most common causes of infection include:

  • Poor hygiene
  • Cosmetic products that contain harsh chemicals
  • Extended periods of moist conditions underarm
  • Excessive sweating or hyperhidrosis

The treatment of the infection depends on the underlying cause. If the condition occurred due to excessive sweating, your doctor might prescribe oral or topical drugs, antibiotics, and over-the-counter pain relievers.

It is essential to use high-quality deodorants that do not contain harsh chemicals. Always keep your underarms dry and clean to prevent sweat, oil, and bacteria from building up on your skin.

11. Breast Infection

Breast infections are commonly caused by Staphylococcus aureus, a type of bacteria found on the skin. The condition occurs when the bacteria penetrate through a crack or break in the skin, resulting in swelling.

This condition, also known as mastitis, occurs in breastfeeding women. A small percentage of infections not associated with breastfeeding are rare forms of breast cancer.

Non-lactational mastitis may occur in women with a compromised immune system. Those who have diabetes or lumpectomies may develop an infection. The common symptoms of breast infection may include:

  • Abnormal swelling of a breast
  • Presence of a painful lump in the affected breast
  • Nipple discharge
  • Burning sensation or pain during breastfeeding
  • Enlarged lymph nodes in the neck or armpits region

Other symptoms may include warm breasts, chills, redness, fever, breast tenderness, and nipple discharge. If you are experiencing pain in the left armpit and some of the symptoms of a breast infection, contact your doctor for a proper diagnosis. During your treatment, you can also perform home remedies to relieve discomfort.

12. Pleurisy

The lining of the lung and chest area may become inflamed. This may be caused by a wide variety of health conditions, such as pneumonia, respiratory problems, and exposure to chemicals that may be toxic to the body.

The main reason why this condition is called pleurisy is that the lung and chest area is called “pleura.” Like Costochronditis, the pain brought about by this condition may increase whenever there is any type of movement. For example, if you try to breathe deeply, this will make you feel a sharp pain in the left armpit.

13. Shoulder Dislocation

One of the possible causes of pain in the left armpit is the dislocated shoulder. A partial dislocation occurs when the humerus (top of the upper arm bone) is partially out of the glenoid (joint socket). When the humerus is out of its socket, it is a complete dislocation. The symptoms of a dislocated shoulder include:

  • Swelling
  • Deformity
  • Numbness
  • Bruising
  • Weakness

Dislocation of the bone may damage ligaments and nerves around the area. If you experience any of the symptoms mentioned, visit a specialist immediately. The doctor will place the humerus (upper arm bone) back into the glenoid (joint socket). They may also immobilize the shoulder for a few weeks.

You can also cool the area with ice three to four times daily to alleviate inflammation and pain. Once the swelling goes down, your doctor will prescribe rehabilitation exercises to strengthen the muscles and restore the range of motion.

14. Cerebrovascular Accident / Stroke

A cerebrovascular accident or stroke occurs when blood flow to a part of the brain is restricted by a blood vessel or blockage rupture. If you suspect that you or someone you know might have stroke symptoms, make sure you visit a doctor quickly. Leaving it untreated for too long can cause permanent damage to the brain. The symptoms of a stroke are:

  • Difficulty walking
  • Dizziness, blurred vision
  • Loss of coordination and balance
  • Paralysis or numbness in the arm, leg, or face
  • A sudden headache, usually accompanied by dizziness, nausea, and vomiting
  • Difficulty speaking or understanding

If any of the symptoms are present, it is essential to go to a fast prognosis and treatment hospital. Your doctor will perform tests to discover the cause and determine its location. Treatment will depend on the type of stroke.

To reduce your risk, limit cholesterol and saturated fat consumption. Maintain blood pressure, control diabetes, eat a diet rich in fruits and vegetables, and get regular exercise. Do not drink alcohol excessively, and refrain from smoking.

15. Brachial Plexus Injury

Another possible cause of pain in the left armpit is brachial plexus injury. This condition occurs when the network of nerves that delivers signals from the spine to shoulders, arms, and hands are compressed, stretched, or torn. In minor cases, brachial plexus injuries are caused by contact sports, such as wrestling and football. However, tumors or inflammation may also lead to damage.

Severe brachial plexus injuries are caused by motorcycle or auto accidents and may leave the arm paralyzed. Surgical procedures will be required to restore sensation and function. Depending on the location and severity of the injury, the signs and symptoms of this condition are:

  • Minor injuries – Burning sensation or electric shock shooting down the arm, weakness, and These symptoms may last for a few seconds to several minutes.
  • Severe injuries include weakness, inability to use your shoulder, arm, or hand, and severe pain.

See a doctor if you experience weakness in your arm or hand, neck pain, and other symptoms of brachial plexus injuries. It is crucial to be treated immediately after the damage as it can result in permanent weakness or disability.

16. Hyperthyroidism

Overactive thyroid or hyperthyroidism is a condition in which the thyroid gland produces excessive hormone thyroxine. This significantly boosts the body’s metabolism and leads to irregular heartbeat, sudden weight loss, irritability, nervousness, and sweating. In some cases, it may also cause pain in the left armpit. The common symptoms of hyperthyroidism include:

  • Sudden weight loss
  • Increased appetite
  • Rapid or irregular heartbeat
  • Trembling fingers
  • Frequent bowel movements
  • Brittle hair and thinning skin
  • Anxiety, irritability, and nervousness

Other symptoms of hyperthyroidism include sweating, increased sensitivity to heat, changes in menstrual patterns, muscle weakness, and fatigue. Treatment depends on the physical condition, age, severity, and underlying cause. Your doctor may recommend anti-thyroid medications, radioactive iodine, beta-blockers, or surgery.

17. Pinched Nerve

The Pinch nerve could also cause pain in the left armpit. It occurs when excessive pressure is applied to the affected Nerve by surrounding tissues, such as muscles, bones, tendons, or cartilage. Other health conditions may lead to pinched nerves, such as obesity, sports activities, injury, repetitive work, wrist arthritis, or rheumatoid.

The signs and symptoms may include:

  • Pins and needles or tingling sensations
  • Reduced sensation or numbness in the area
  • Burning, aching, or sharp pain
  • Feeling that your hand does not function properly.

In most cases, conditions related to a pinched nerve are worse at night. See a specialist immediately if you have experienced the signs and symptoms for a few days. The most recommended treatment for a pinched nerve is rest. Avoid any activities that can aggravate the condition. Your doctor may also recommend physical therapy and medications. Surgery may be required if the condition does not improve.

18. Cyst

A cyst in your armpit may sound scary, but it does not pose a life-threatening condition. Cysts can develop anywhere in the body. They are more likely to appear on the skin and be filled with pus, fluid, or air. Most cysts are usually harmless and caused by infections or blocked glands.

The common causes of armpit cysts are:

  • Shaving
  • Bacterial, fungal, or viral infection
  • Fibrocystic breast changes
  • Lipoma
  • Vaccination
  • Hidradenitis Suppurativa

In rare cases, a cyst in the armpit could be caused by cat scratch fever, mononucleosis, AIDS, and cancer. If the pain is not severe, you can try home remedies to eliminate the cyst. If the cyst and surrounding area are inflamed, visit a doctor to have it appropriately examined. Your doctor may recommend injecting steroids to alleviate the inflammation.

How to Treat Pain in Left Armpit

If the pain is mild or while waiting for your appointment, you can try simple remedies to reduce the pain.

  • A cold compress or cold water can help you reduce itchiness and inflammation.
  • Take a warm bath and add one tablespoon of baking soda to treat pain, itchiness, inflammation, and lumps.
  • Practice good hygiene by washing your underarms with antibacterial soap and warm water.
  • Massage the affected area gently to reduce swelling and improve blood circulation.
  • Avoid spicy and oily foods, as these can make you sweat. Eat more vegetables and fruits instead.

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