Most lumps are harmless and are usually the result of abnormal tissue growth. However, armpit lumps can be related to a more serious underlying health problem.

You should have your doctor evaluate any unusual lumps you have.

The most common causes of armpit lumps are:

• bacterial or viral infections
• lipomas (typically harmless, benign fat tissue growths)
• a fibroadenoma (a non-cancerous fibrous tissue growth)
• hidradenitis suppurativa
• allergic reactions
• adverse reactions to vaccinations
• fungal infections
• breast cancer
• lymphoma (cancer of the lymphatic system)
• leukaemia (cancer of the blood cells)
• systemic lupus erythematosus (an autoimmune disease that targets your joints and organs)

Armpit lumps can occur in men and women of all ages. However, a lump under the arm may indicate breast cancer.

Women should perform monthly breast self-examinations and report any breast lumps to a doctor right away.

For the most accurate results, women should perform breast self-exams about one to three days after your period ends as the breasts undergo hormonal changes during the menstrual cycle and may tend to feel more tender or lumpy during this time – which is considered completely normal during this time.

Another potential cause of armpit lumps in women, which tend to also occur near the breast and groin regions, is hidradenitis suppurativa.

This chronic condition involves clogging and inflammation near the glands of hair follicles in the skin, commonly causing painful boil-like lumps that can fill with pus, leak, and can become infected.

An armpit lump may feel small. In other cases, it may be extremely noticeable. Armpit lumps may be caused by cysts, infection, or irritation due to shaving or antiperspirant use. However, these lumps may also indicate a serious underlying health condition.

Seek medical attention if you have an armpit lump that gradually becomes enlarged, is or isn’t painful, or doesn’t go away.

The course of treatment your doctor recommends depends on the underlying cause of the lump. Bacterial infections can be treated with oral antibiotics.

After several days, the armpit lump should start to disappear as your body and the antibiotic fight the infection.

If your lump is associated with allergies, it should subside once you start medication and learn to avoid your allergy triggers.

In most cases, armpit lumps don’t require any treatment, just simple observation. If your doctor determines this is the case, you can use home remedies such as warm compresses and over-the-counter pain relievers to ease any discomfort.

Lumps that don’t require treatment include those associated with:

• lipomas (fat-containing lesions)
• viral infections
• fibroadenoma (noncancerous breast lumps)

Hidradenitis suppurativa treatment options may include some of the following:

• antibiotic therapy
• bleach bath
• biologic therapy
• wound dressings
• anti-acne therapy
• surgical treatment
• lifestyle changes

If your armpit lumps are cancerous, your doctor may refer you to a specialist for further care.

Treatment will depend on the type of cancer and what stage you’re in, and it may involve a combination of:

• chemotherapy
• radiation therapy
• surgery