Your armpit undergoes a lot throughout the day, from sweats to shaving, and some might add rigorous washing to the list too. With so much physical exertion, you should not wonder, “why does my armpit hurt?” Well, since there is so much involvement of activity in that area, the reasons for pain in the armpit vary, from simple muscle strain to something as grave as cancer. It is better that you schedule a checkup if you feel suspicious about your pain or in case you have stings in the left armpit.

Causes For Pain In the Armpit

Here are some common reasons why your armpit either left or right side, undergoes pain.

Boils/Ingrown Hair – Skin Irritation

Your skin of the armpit faces constant contact, which may result in rashes, skin tenderness, pain in the armpit or overall itchiness. The reason for this skin trouble may be the presence of a boil because of ingrown hair.

Muscle Strain

You are most likely to suffer from pain under your armpit in case of the habitual heavy lifting of objects, intense workouts, sudden motions etc. The main symptoms you experience are swelling or bruising in the upper rib cage or arms with a tender shoulder and pain in the armpit.

Lymph Nodes – Swollen

The primary purpose of lymph nodes is fluid and waste product drainage from other parts of the body. Lymph nodes also play their role in combating infections and may grow in size while doing so. Therefore, if you have pain in the armpit with a swollen lymph node, it is most likely due to an infection.

Angina Pectoris

Cardiac blood flow faces reduction because of angina pectoris. This situation arises when the blood vessels (arteries) narrow up, forcing the heart to pump with extensive pressure to deliver blood around the body. If you feel a sudden sharp pain in the left armpit, get it checked immediately since the issue may progress into a heart attack.


An autoimmune disorder that affects various parts of the skin alongside the armpits. In this condition, scaling, itching and discomfort is common.

Fungal Or Bacterial Manifestation

Ringworm is a fungal infection seen in the skin’s upper layer and characterizes with a ring-shaped red rash. Armpits are the perfect location for fungal growth since it is humid and moist most of the time because of sweating. All of these factors help multiply bacterial and fungal growth, causing inflammation and bump in the armpit leading to pain.


It is a type of inflammation because of moisture and friction in the creases of the armpit skin. Intertrigo presents itself with redness, pain or burning feeling; moreover, it may smell bad too.


Your lymph nodes in the upper body and the armpit become extra hard if you develop cancer.

Cystic Growth

Fluid buildup in the armpit is because of bacterial presence, and they cause immense pain on touch.


Visiting the ER for pain under your armpits is a good decision if you have one or more of the following symptoms:

  • Pain in the armpit left side of the chest area
  • Fever
  • If any part of your body is draining pus
  • Difficulty in breathing
  • SOB

If you find any unusual protrusion or bump growth in the armpit; head to Internal Medicine and Diagnostic Center for help. Visit us by making an appointment at (281) 252-8600.

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