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)

In England, AAA screening is routinely offered to men once they turn 65. This is because men aged 65 and over are most at risk of developing an AAA.

Others at an increased risk of an AAA include:

• Men or women with a parent, child, or sibling who also has an AAA
• Patients with high blood pressure
• Smokers and ex-smokers

Men under the age of 65 and women are typically less likely to develop an AAA, but if you’re concerned and haven’t been offered a scan, you can request one.

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