9 Unexpected Reasons Why You Have Lump in Your Armpit

9 Unexpected Reasons Why You Have Lump in Your Armpit

Are lumps under armpits normal? Lump in the armpit is not a normal occurrence. There are so many reasons why you can feel a lump in your armpit when applying a cream to your body or when doing a self-breast exam. Some of the reasons are cancerous in nature, infectious causes, or allergic reactions. Lumps can be hard, soft, painful, mobile, or not mobile, depending on the cause of the lump. 

Lump in the armpit can occur in both men and women of all ages.

What causes a lump under the armpit?


Boils are infections of the hair follicles that cause a painful, swollen area underneath the skin that is made up of an accumulation of dead tissue and pus. When only a single boil is present, it is called a furuncle, but when boils are clustered together in their multiples, it is called carbuncles. Staphylococcus aureus bacteria usually cause boils. Fever, fatigue, and swollen lymph nodes are some of the manifestations of severe infection.

Breast cancer

Breast cancer is an abnormal malignant growth of cells that develops from the breast tissue and can spread to other tissues. Some of the indications are swollen lymph nodes in the armpit, bone pain, lump in the breast, change of breast shape, dimpling of the skin, nipple discharge, red/scaly parches of the skin and inverted nipples. Here are warning signs of breast cancer

Risk factors for developing breast cancer are:

  • Genetics (family history of breast cancer)
  • Sex: female
  • Hormonal replacement therapy
  • Early age of menarche
  • Alcoholism
  • Obesity
  • Previous breast cancer


A lipoma is a benign tumor formed of fat tissue that is soft, painless, and movable. Most lipomas are less than 5cm in size, and they are most common in the armpit, shoulder, stomach, and upper back region. 

Risk factors of lipoma include:

  • Obesity.
  • Lack of exercise.
  • Family history of lipoma.
  • Hypercholesteremia.

Skin cyst

A skin cyst is a small isolated sac of fluid or pus that can form anywhere in the body. Cysts can happen as a result of trauma, ingrown hair, using antiperspirants, or irritation from shaving.


Lymphedema is likewise known as the lymphatic obstruction, is a localized swelling in the arm or leg that is caused by a lymphatic system blockage. Lymphedema is most commonly caused by the removal of lymph nodes, damage to the lymph nodes as a result of the cancer treatment regimen, or parasitic infections.

Bites from insects

Bite from an insect such as a mosquito or tsetse fly can cause the different sizes of red bumps to form underneath the arm. These kinds of bumps are extremely itchy and can become sores when scratched.

Blocked milk ducts

Milk ducts can become blocked in nursing mothers, and this can cause a lumpy swelling in the area of the breast and the armpit.


Vaccines are beneficial lines of medications that are good for preventing several diseases. Certain vaccines cause swollen lymph nodes in the armpit, and the swelling can becomes uncomfortable. (Tell your health care provider if you noticed a swollen lymph node after vaccination).

Hodgkin’s lymphoma

Hodgkin’s lymphoma is a cancer of the lymphatic system, which is characterized by swelling of lymph nodes in the armpit, groin, and neck.

Diagnostic methods to the diagnosed cause of armpit lumps are:

  • Neck X-ray
  • Full blood count.
  • Microscopy/culture/sensitivity.
  • CT scan.
  • MRI scan.
  • Lymph node biopsy.
  • Bone marrow biopsy.
  • Mammogram.

How do you treat armpit lumps?

Treatment of armpit lumps is carried out based on the underlying reason for the lump. In most instances, armpit lumps don’t require treatment, just as warm compresses and over-the-counter pain to help relievers any pain. 

When should I go to the doctor for a lump in my armpit? It is advisable to see your doctor for medical examinations as soon as possible to rule out any severe causes.