Armpit Swelling or Armpit Lump: 10 Common Causes

Armpit swelling, also known as axillary swelling, refers to the lump or bump in the armpit or underarm area. Some armpit lumps are painless, and others may cause swelling. In addition to the swelling, some other symptoms include fever, tenderness, soreness, or swollen lymph nodes in the neck.

Armpit swelling is a common condition with several possible causes. A swollen lymph node or gland under the armpit is the most common reason. Skin irritation, such as shaving, can also cause armpit swelling or armpit lump.

Most lumps that cause swelling are not severe, but serious diseases may cause some swelling. Although both men and women may suffer from armpit lumps, women should pay more attention to them because they may indicate breast cancer.

Women should have a regular breast examination every month. If you find a lump in the armpit, consult your doctor immediately. A man should also pay attention to this condition. If the unexplained bumps become larger or don’t go away for a long time, please see your doctor immediately.

Armpit Swelling or Lump
Armpit Swelling or Armpit Lump: 8 Common Causes with Treatment

10 Common Causes of Armpit Swelling or Armpit Lump

There are many reasons for Armpit Swelling or Armpit Lump. The following are the 8 most common causes.

1. Swollen lymph node

A swollen lymph node is one of the most common reasons for armpit swelling or armpit lump. You have lymph nodes in many areas of your body, including the neck, groin, and armpits. They are filters for the lymph system that can help trap viruses and bacteria.

The swollen and painful lymph node is usually a sign that your immune system is fighting an infection. Common causes of swollen lymph nodes include strep throat, a cold, measles, ear, tooth, or wound infections. HIV, Vaccine reactions, mastitis, or an abscess can also lead to swollen lymph nodes. In addition to pain, swollen lymph nodes can cause fever, night sweats, runny nose, and sore throat.

In most cases, swelling of the lymph nodes occurs on both sides of the body; this is a normal response to infection. In some cases, swollen lymph nodes may occur on one side. This could be a sign of a tumor or breast cancer.

If you experience severely swollen lymph nodes, please seek medical help immediately. These severe symptoms include unexplained weight loss, high fever, feel hard or rubbery when pressing them.

2. Viral or bacterial infections

Both bacteria and viruses can invade your body’s cells and lead to infections. This will cause swollen lymph nodes and armpit swelling.

Antibiotics can be used to treat bacterial infections, but there’s no specific treatment for viral infections. There are some home remedies to relieve aches, pains, and fevers. These methods include getting plenty of rest, drinking plenty of water, and taking some OTC pain medications, such as acetaminophen.

3. Muscle Strain

There are many blood vessels, nerves, and muscles in the armpits. These muscles can help the arm move. However, exercising too much or lifting heavy objects can easily cause axillary muscle strain.

Muscle strains can usually cause swelling, redness, cramps, and pain in the armpits, especially after exercises that stretch the muscles.

A mild muscle strain can be relieved by rest. In addition, some home remedies can also help relieve swollen armpits. You can wrap the ice cube in a towel and place it on the painful area to reduce swelling. Please consult your doctor if the strain does not heal, or the symptoms worsen within a few weeks.

4. Skin irritation

Skin irritation is also one of the common causes of swelling in the armpits. These skin-irritating behaviors include shaving armpit hair, scratching, and friction from wearing tight clothing. In addition, hormonal fluctuations or ingrown hair can also cause skin irritation and lead to swelling of the armpits.

5. Breast cancer

Breast cancer is a type of tumor that occurs when the cells in the breast grow uncontrollably. This condition can cause pain and swelling in the armpits. This pain usually comes before you feel a lump in your breast.

Therefore, if you suspect that the symptoms are caused by breast cancer, please see a doctor as soon as possible. The treatments for breast cancer include chemotherapy, radiation therapy, and surgery.

6. Ingrown hair

Ingrown hair can clog sweat glands and cause skin infections. This will cause swelling of the underarm skin. To reduce the symptoms of ingrown hair, stop shaving, using tweezers, or waxing immediately until the condition improves.

In addition, some other methods, such as laser treatment, can also help remove hair at a deeper level and inhibit regrowth. However, be aware that this may cause scars, blisters, and skin darkening.

7. Fibroadenoma or lipomas

Fibroadenoma refers to noncancerous fibrous tissue growth. A lipoma is the uncontrolled growth of fat. This condition can lead to armpit swelling or a lump. In addition, some other diseases, such as leukemia or lupus, can also cause swelling of the underarm skin.

8. Allergic reactions

Some allergic reactions can also cause armpit swelling. Common allergens include deodorant, antiperspirant, or soap. If you notice symptoms of swollen armpits, you need to remove these allergens immediately.

9. Skin cyst

A cyst is a small sac or lump filled with fluid that can form almost anywhere in the body. This condition is not contagious. It is usually caused by trauma or irritation such as ingrown hair, shaving, or an antiperspirant.

Cysts are usually painless unless they are infected. An infected cyst can cause armpit swelling, redness, and pus. These cysts are most common in acne patients over 18 years of age. You do not need to care for a small cyst though it is unsightly. An infected cyst should be treated to prevent the spread of infection.

10. Insect bites

An insect bite, especially a mosquito bite, can cause painful, reddened clusters of bumps under your arm. These lumps are usually very itchy and may lead to inflammation of sweat glands. You can relieve pain and itching by applying some ointment.

Treatment For Armpit Swelling or Lump

The treatment of armpit lumps depends on the different causes. Some armpit lumps do not require treatment and will disappear after a while. For example, armpit lumps caused by a viral infection will disappear as the infection clears up. Lumps caused by allergic reactions usually go away once the allergen is removed.

In addition, some mild symptoms can be treated with home remedies. Hot compresses can help relieve swelling and pain. In addition, taking painkillers such as ibuprofen can help relieve symptoms. Note that if a bacterial infection causes the bump, you need to remove the allergen first.

For some severe conditions such as lipoma or breast cancer, surgery or chemotherapy is often required.

When to see a doctor

Swelling or lumps under the armpits are widespread, and not all lumps are harmful. But if there are some serious symptoms, please seek medical help immediately. These symptoms include:

  • Gradually enlarged lumps under the armpit
  • No pain after squeezing
  • Unexplained armpits swelling
  • It lasts for a long time and does not go away


As with all types of diseases, early detection is essential for treatment. Therefore, it is crucial to determine the cause of the armpit lump. When armpit swelling or lump is discovered, you should consult your doctor to determine the exact reason as soon as possible.

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