What does pain under the left armpit mean in females?

Pain in your left armpit or the left side of your breast and armpit may indicate a straightforward issue that clears up with rest, such as a muscle strain, or it could be a symptom of a more serious condition, such as cancer or heart disease.

Some causes of armpit pain can affect anyone regardless of sex or gender, but some might be specific to women, such as those related to hormonal changes seen in females or people who menstruate.

Sex and gender exist on spectrums. This article uses the terms “women,” “men,” or both when discussing people assigned female or male at birth to reflect language that appears in source materials. 

While gender is solely about how you identify yourself, independent of your physical body, you may need to consider how your personal circumstances will affect diagnosis, symptoms, and treatment. 

What could be causing pain under your left armpit?

Unless the cause of your pain is obvious, such as an injury or trauma to the armpit area, talk with a doctor or healthcare professional if you have unexplained pain in your armpit or the side of your breast.

Several things could cause pain in this area, and the chances are that it will not be anything serious. But in some cases, it may indicate a serious medical issue.

Joint or muscle pain

Certain exercises can strain the muscles or joints under your arms. Strain to the pectoral muscles in your chest can also cause armpit pain.

If you’re experiencing armpit pain, consider whether you have done any exercises or activities lately that could have strained your muscles or joints, such as lifting heavy weights or moving home.

These injuries will likely heal on their own with time. Avoid lifting anything too heavy while your armpit heals.

Skin infections or inflammation

An infection or inflammation in the skin or tissues under your arm may cause pain or discomfort. Bacteria, viruses, or fungi can cause infections in your armpit or the left side of your breast. Autoimmune diseases may cause inflammation.

• Hidradenitis suppurativa is a chronic skin condition that mostly appears in areas with frequent skin-on-skin contact, such as the armpit. Painful nodules appear, and you may develop abscesses in the area.
• Psoriasis is an autoimmune skin disease that may cause red scaly plaques or blisters on your skin. It can occur anywhere on your body, including your armpit.
• Sporotrichosis is a fungal infection that may infect your skin or deeper organs.
• Shingles is a painful rash resulting from the herpes zoster virus. In addition to shooting, burning pain, you may also have fluid-filled blisters, or your skin may itch, tingle, or feel numb. It usually only affects one side of your body, so you may notice pain in only your left armpit.

Breast pain

You might experience pain on the left side of your breast to under your armpit. Breast pain is known as mastalgia, and it can affect any part of your breasts, including around the edges near your armpit. You may feel like the pain is coming from your armpit, and it may be constant or come and go.

If your breast pain happens in cycles, it is likely linked to your period and the hormonal changes that happen throughout your cycle.

Allergic reactions or irritation

Rashes or irritation from allergies or other irritants may cause discomfort under your arms. Irritants may include:

• lotions or deodorants
• excessive heat or sweating
• rubbing or stress from tight clothing or bag straps
• shaving or waxing

Pressure against the tissues and nerves

Anything that pushes against the tissues and nerves under your arm or along the left side of your breast may cause discomfort or pain. 

• Lymphadenopathy happens when your lymph nodes begin to swell. Swollen lymph nodes under your arm may indicate an infection, an autoimmune disease, or cancer.
• Cysts may form under your arms and push on the underlying tissues and nerves. 
• Degeneration of the connective tissue in the joint, swelling from injuries in the area, or using crutches may damage muscles or lead to nerve damage.
• Breast cancer may lead to breast or underarm pain if cancer cells begin to press against the tissues and nerves under the arm.

Heart conditions

Chest pain that also affects your armpit and radiates down your left arm may indicate a heart condition. You may have pain in your chest, arm, or both. 

A few serious conditions could cause this type of pain.

• Angina or chest pain may occur when your heart muscle lacks oxygen. It is the most common symptom of a blocked artery in your heart.
• A heart attack occurs when oxygen does not reach a part of your heart, and your heart muscle begins to die. This is commonly associated with pain in your left arm.
• Peripheral artery disease (PAD) occurs when an artery supplying blood to your body is partially or entirely blocked, and blood cannot reach a particular area. If the blood flow to your arm is blocked, you may have pain in the area.

Chest pain is a medical emergency. Call 911 if you or someone near you is having chest pains, especially if you also have:

• difficulty breathing
• excessive sweating
• nausea or vomiting
• pain radiating to one or both arms, your jaw, or your back

It’s also important to note that women tend to experience different heart attack symptoms to men.

Stroke

You may have pain in one or both arms after a stroke, especially one that has left one side of the body weaker or unable to move. External forces place extra stress on your limbs, especially the shoulders.

This force may be as simple as gravity pulling down on the limb. The joint may become partially dislocated if your arm is not supported after a stroke.

Pleurisy

Pleurisy is inflammation of the lining around the outside of the lungs. It may occur due to lung disease or an infection elsewhere in your body that spreads to the lung lining. Symptoms of pleurisy include:

• sharp pain in the chest or shoulder made worse by breathing, sneezing, or coughing
• pain that feels dull, burning, or “catches” during a breath

Treatment options

A doctor or healthcare professional will treat your armpit pain based on its cause.

• They may need to reset your shoulder if you have a shoulder injury. In severe cases, you may need surgery.
• A doctor may recommend nitroglycerin or aspirin for chest or arm pain caused by heart disease.
• If you have a bacterial infection, your doctor may give you antibiotics such as amoxicillin or cephalexin.
• For fungal infections like sporotrichosis, you may need an antifungal medication like itraconazole.
• Viral infections like shingles may need antivirals, such as acyclovir or valacyclovir. Your doctor may also prescribe gabapentin for nerve pain.
• If you have something pressing against the armpit area, such as a cyst or a tumor, a surgeon may need to remove it. 

If an autoimmune disease, such as psoriasis, is causing the pain, your doctor may prescribe medications that suppress your immune system and reduce inflammation. These may include prednisone (Rayos), hydrocortisone (Cortef), or methotrexate (Trexall).

For general pain due to any of these conditions, a doctor may also recommend mild pain relievers alongside your other treatments, such as:

• acetaminophen (Tylenol)
• ibuprofen (Advil or Motrin)
• naproxen (Aleve)

For more severe pain, they may prescribe opioids, such as oxycodone. This is usually a last resort option if the pain is very severe and you’re unable to manage it with other methods.

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When to contact a doctor

Talk with a doctor or healthcare professional about your unexplained underarm pain if: 

• it does not go away after a few days of rest
• it develops a painful rash or blisters
• you notice a nodule or bump under the skin
• it affects your breathing
• you develop numbness, tingling, or loss of sensation in your arm

Call 911 immediately if symptoms also include: 

• chest, back, or jaw pain
• difficulty breathing
• nausea or vomiting
• dizziness

Summary

There could be several reasons for a female to experience pain in their left armpit. This could be an injury, skin condition, or other health condition.

It is not usually serious, but if you experience any accompanying symptoms, like arm pain, dizziness, or nausea, contact 911 as soon as possible, as this could be heart-related.

A healthcare team can consider your symptoms and prescribe the best treatment for you.

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