Pain in your left armpit or the left side of your breast and armpit may indicate a straightforward issue that clears up with rest, or it could be a symptom of a more serious condition, such as cancer or heart disease.
What could the pain be?
Unless the cause of your pain is obvious, such as an injury or trauma to the armpit area, you should 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.
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 underarm. 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.
- 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.
Anxiety and stress
A 2016 review suggests a possible relationship between arm pain and stress, but there is not enough evidence to prove that stress is a risk factor for chronic underarm pain.
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.
- 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
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.
For mild pain due to nerve, muscle, or tissue damage, a doctor may recommend mild pain relievers, such as
For more severe pain, they may prescribe opioids, such as oxycodone.
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).
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